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 [Search a list of Patent Appplications for class 181]   CLASS 181,ACOUSTICS
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SECTION I - CLASS DEFINITION

This class includes devices and corresponding methods for mechanically transmitting, for amplifying and for ascertaining the direction of sound and for mechanically muffling or filtering sound, and not elsewhere provided for.

SECTION II - REFERENCES TO OTHER CLASSES

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73Measuring and Testing,   subclasses 572+ and especially 645+ for the determination of qualities, characteristics or conditions by the utilization of acoustical energy and which is not specifically provided for elsewhere.
84Music,   appropriate subclasses for musical instruments.
109Safes, Bank Protection, or a Related Device,   subclass 21.5 for partitions having a sound transmitting passage constructed to prevent passage of projectiles.
116Signals and Indicators,   appropriate subclasses, for mechanical signaling devices utilizing sound.
178Telegraphy,   appropriate subclasses, for acoustic instruments limited to that art.
333Wave Transmission Lines and Networks,   subclasses 141+ for electrical delay networks wherein the electrical waves may be converted to sound waves, such sound waves being delayed and reconverted to electrical waves, and subclasses 186+ for wave filters of the electromechanical transducer type, wherein electrical waves may be converted to sound waves, such sound waves being filtered and reconverted to electrical waves.
352Optics: Motion Pictures,   subclasses 1+ for "taking" motion picture apparatus.
367Communications, Electrical: Acoustic Wave Systems and Devices,   for electrical signaling devices utilizing sound or compressional waves.
369Dynamic Information Storage or Retrieval,   for an information storage or retrieval device having particular acoustical structure.
379Telephonic Communications,   appropriate subclasses, for acoustic instruments limited to that art.
381Electrical Audio Signal Processing Systems and Devices,   appropriate subclasses for one-way electrical transmission of audio signals.
434Education and Demonstration,   particularly subclass 300 , on teaching acoustic principles.
446Amusement Devices: Toys,   subclass 175 for a toy having sound responsive switch or control.
472Amusement Devices,   particularly subclass 64 for an amusement device causing an illusion by sound imitation or effect.
505Superconductor Technology: Apparatus, Material, Process,   subclasses 150+ for high temperature (Tc 30 K) superconducting devices, and particularly subclass 203 for electroacoustic transducers.

SUBCLASSES

[List of Patents for class 181 subclass .5]    .5MISCELLANEOUS:
 This subclass is indented under the class definition.  Inventions falling within the definition of this class, and not otherwise provided for.
(1) Note. Acoustic levitation devices are found here.

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73Measuring and Testing,   subclasses 570+ for an acoustic levitation apparatus combined with a motion sensing device or a motion controlling device and not elsewhere classified.
  
[List of Patents for class 181 subclass 18]    18Systems:
 This subclass is indented under subclass .5.  Construction of speaking-tubes with their associated parts; also "speaking-tube exchanges", also, any patents on speaking-tubes not classified elsewhere.
  
[List of Patents for class 181 subclass 19]    19Alarms and indicators:
 This subclass is indented under subclass .5.  Alarms or indicators of a speaking-tube.
  
[List of Patents for class 181 subclass 20]    20Combined mouth and ear pieces:
 This subclass is indented under subclass .5.  Mouthpieces and connected earpieces.
  
[List of Patents for class 181 subclass 21]    21Mouthpieces:
 This subclass is indented under subclass .5.  Structure of the mouthpieces of speaking-tubes and the combination therewith of accessory parts, as alarms, indicators, etc.
  
[List of Patents for class 181 subclass 22]    22Tubes:
 This subclass is indented under subclass .5.  The construction of the tubes, per se.
  
[List of Patents for class 181 subclass 30]    30AUDITORIUM:
 This subclass is indented under the class definition.  Devices for improving the acoustic properties of halls or other places.
  
[List of Patents for class 181 subclass 101]    101GEOPHYSICAL OR SUBSURFACE EXPLORATION:
 This subclass is indented under the class definition.  Subject matter relating to systems for mechanically transmitting or receiving acoustical waves for the purpose of identifying geologic or subsurface structure.
(1) Note. Subsurface is defined as including anything, whether composition, article, structure or formation which lies below the upper natural surface of the earth.
(2) Note. Acoustical waves are considered to include seismic waves for the purposes of this section.
(3) Note. In scope, this subclass is analogous to Class 367 Communications Electrical: Acoustic Wave Systems and Devices subclasses 25+ and 853.1+ wherein electrical communication, in part or in whole, is involved.

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124,for depth sounding related to sound echo compressional wave systems.

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324Electricity: Measuring and Testing,   subclasses 323+ for geophysical surface or subsurface exploration in situ generally.
340Communications: Electrical,   subclass 853.8 for a wellbore telemetering system.
367Communications, Electrical: Acoustic Wave Systems and Devices,   subclasses 14+ for seismic prospecting using electrical acoustic wave systems.
  
[List of Patents for class 181 subclass 102]    102Well logging:
 This subclass is indented under subclass 101.  Subject matter wherein said geologic or subsurface structure includes a shaft or deep boring in the earth.

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33Geometrical Instruments,   subclasses 302 and 304+ for bore-hole direction indicators.
73Measuring and Testing,   subclasses 152.01+ for instruments, for bore-hole studies.
166Wells,   subclasses 64 , 66 and 113 for well apparatus including measuring and testing means, subclasses 250.01+ for well processes including measuring and testing, and subclass 264 for processes comprising merely sampling a well fluid and appropriate subclasses (especially subclasses 142+ and the subclasses there noted) for the corresponding apparatus.
175Boring or Penetrating the Earth,   subclasses 40+ for a process or means of measuring or testing combined with an earth boring process or apparatus.
250Radiant Energy,   subclasses 256+ for ray energy detection or measurement (including detection or measurement of radioactive materials) applied to bore-hole and drilling study.
324Electricity: Measuring and Testing,   subclasses 323+ for electrical testing of bore holes.
340Communications: Electrical,   subclasses 853.1+ for telemetering in wells.
367Communications, Electrical: Acoustic Wave Systems and Devices,   subclasses 25+ for seismic well logging using acoustic wave responsive electrical means.
  
[List of Patents for class 181 subclass 103]    103Programmed or timer-controlled:
 This subclass is indented under subclass 102.  Subject matter including means operative upon initiation to transmit or receive acoustical waves through a given cycle of operations.

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107,for similar subject matter not limited to a well bore.
  
[List of Patents for class 181 subclass 104]    104Directional source or detector:
 This subclass is indented under subclass 102.  Subject matter including means for sending, or receiving acoustical waves which is characterized by some quality that varies according to the relative bearing of the means.

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125,for sound locating means not limited to bore holes.
  
[List of Patents for class 181 subclass 105]    105Bore hole or casing condition:
 This subclass is indented under subclass 102.  Subject matter for investigating physical conditions of well bores and casings, such as obstructions, bore surfaces, etc.

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73Measuring and Testing,   subclasses 152.01+ for a determination of a physical characteristic of a borehole by making a measurement which is not purely electrical or purely magnetic and subclass 152.57 for a determination of a physical characteristic of a casing or a cementing by making a measurement which is neither purely magnetic.
  
[List of Patents for class 181 subclass 106]    106Seismic wave generation:
 This subclass is indented under subclass 102.  Subject matter including means for generating acoustical waves mechanically in the shaft.

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108+,for seismic wave generation not limited to a well bore in combination with a receiver.
133+,for seismic wave generation not limited to a well bore.

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73Measuring and Testing,   subclasses 152.01+ for a determination of a physical characteristic of a borehole by making a measurement which is not purely electrical or purely magnetic and subclass 152.57 for a determination of a physical characteristic of a casing or a cementing by making a measurement which is neither purely electrical nor purely magnetic.
  
[List of Patents for class 181 subclass 107]    107Programmed or timer-controlled:
 This subclass is indented under subclass 101.  Subject matter including means operative upon initiation to transmit or receive acoustical waves through a given cycle of operations.

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103,for this subject matter in a well bore environment.
  
[List of Patents for class 181 subclass 108]    108Seismic source and detector:
 This subclass is indented under subclass 101.  Subject matter including means for transmitting and receiving seismic waves.
  
[List of Patents for class 181 subclass 109]    109Aerial:
 This subclass is indented under subclass 108.  Subject matter wherein the means for transmitting or receiving seismic waves is elevated above the surface of the earth.
  
[List of Patents for class 181 subclass 110]    110Underwater:
 This subclass is indented under subclass 108.  Subject matter wherein the means for transmitting or receiving seismic waves is in wave coupling relationship with a body of water.
  
[List of Patents for class 181 subclass 111]    111Plural sources:
 This subclass is indented under subclass 108.  Subject matter wherein the means for transmitting seismic waves includes more than one source.
  
[List of Patents for class 181 subclass 112]    112Plural detectors:
 This subclass is indented under subclass 108.  Subject matter wherein the means for receiving seismic waves includes more than one seismic wave detector.
  
[List of Patents for class 181 subclass 113]    113Seismic wave generation:
 This subclass is indented under subclass 101.  Subject matter wherein the system includes means for producing seismic waves.

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116Signals and Indicators,   appropriate subclasses, for mechanical signalling devices utilizing sound.
  
[List of Patents for class 181 subclass 114]    114Vehicle-mounted:
 This subclass is indented under subclass 113.  Subject matter including means for supporting the seismic wave producing means on a land vehicle.
(1) Note. Included in this subclass are combinations of a land vehicle adapted to transport a seismic wave source to a desired location, a seismic wave source, and means to position the source in contact with the earth.
  
[List of Patents for class 181 subclass 115]    115Bubble suppression or control:
 This subclass is indented under subclass 113.  Subject matter including means to minimize adverse effects arising from the production of bubbles by the means for producing seismic waves in a fluid medium.
(1) Note. Some seismic sources produce seismic pulses by producing gaseous bubbles which may produce undesired or adverse secondary impulses. This subclass is drawn to means to mechanically control or compensate for such secondary bubble impulses.
  
[List of Patents for class 181 subclass 116]    116Explosive:
 This subclass is indented under subclass 113.  Subject matter wherein the means for producing seismic waves includes means for utilizing the violent expansion of hot gases resulting from the sudden combustion of a material.
  
[List of Patents for class 181 subclass 117]    117Gas:
 This subclass is indented under subclass 116.  Subject matter wherein the material is a gas.
  
[List of Patents for class 181 subclass 118]    118Underwater:
 This subclass is indented under subclass 117.  Subject matter wherein the seismic waves are produced and coupled to a body of water.
  
[List of Patents for class 181 subclass 119]    119Fluid means:
 This subclass is indented under subclass 113.  Subject matter wherein the seismic waves are generated by utilizing a fluid under pressure.
  
[List of Patents for class 181 subclass 120]    120Underwater:
 This subclass is indented under subclass 119.  Subject matter wherein the seismic waves are produced and coupled to a body of water.
  
[List of Patents for class 181 subclass 121]    121Moving weight:
 This subclass is indented under subclass 113.  Subject matter wherein the seismic waves are generated by utilizing the kinetic energy of a moving inertial mass.
  
[List of Patents for class 181 subclass 122]    122Seismic wave detection:
 This subclass is indented under subclass 101.  Subject matter wherein the system includes means for mechanically receiving the acoustical waves.

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367Communications, Electrical: Acoustic Wave Systems and Devices,   subclasses 140+ for electrical geophysical vibration transducers.
  
[List of Patents for class 181 subclass 123]    123ECHO SYSTEM:
 This subclass is indented under the class definition.  Subject matter having means for sending out a sound wave and receiving said wave after a reflection being utilized to add some information to the original wave.
(1) Note. Except for mechanical altitude or depth detectors in subclass 124 below, this subclass does not provide for mechanical systems relating to identifying geologic or subsurface structure which is provided for by subclass 101 above.

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101+,for systems for identifying geologic or subsurface structure (see (1) Note above).

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73Measuring and Testing,   subclasses 620+ and 627+ for means for testing a body utilizing a wave reflected from a surface of a body.
342Communications: Directive Radio Wave Systems and Devices (e.g., Radar, Radio Navigation),   appropriate subclass for reflected or otherwise returned radio wave systems.
367Communications, Electrical: Acoustic Wave Systems and Devices,   subclasses 87+ for electrical acoustic wave echo systems.
  
[List of Patents for class 181 subclass 124]    124Altitude or depth detection:
 This subclass is indented under subclass 123.  Subject matter for determining the vertical distance of a body above the surface of the earth or the vertical distance down from a surface.
  
[List of Patents for class 181 subclass 125]    125SOUND LOCATION:
 This subclass is indented under the class definition.  Subject matter for ascertaining the direction from which a sound proceeds.

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73Measuring and Testing,   subclass 170.16 for means for measuring cloud height, and subclass 290 for means for measuring liquid level.
342Communications: Directive Radio Wave Systems and Devices (e.g., Radar, Radio Navigation),   subclasses 1 through 205for reflected radiant energy wave systems and subclasses 350+ for radio wave systems.
367Communications, Electrical: Acoustic Wave Systems and Devices,   subclass 87 for electrical echo altimeters, subclass 99 for electrical underwater sound direction indication.
  
[List of Patents for class 181 subclass 126]    126ANATOMIC OR PROSTHETIC RELATION:
 This subclass is indented under the class definition.  Subject matter including an acoustical device wherein at least a portion is in contact with a living being during use.
(1) Note. This and indented subclasses provided for subcombination devices particularly adapted for use in or with the acoustical device.

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600Surgery,   subclass 558 for diagnostics of ear or hearing.
601Surgery: Kinesitherapy,   subclass 47 for kinesitherapy.
  
[List of Patents for class 181 subclass 127]    127Dentiphone:
 This subclass is indented under subclass 126.  Subject matter wherein the acoustical device is held or positioned in the mouth, generally by the teeth.
  
[List of Patents for class 181 subclass 128]    128Ear and mouth:
 This subclass is indented under subclass 126.  Subject matter having an earpiece and mouthpiece operatively connected together.
  
[List of Patents for class 181 subclass 129]    129Ear:
 This subclass is indented under subclass 126.  Subject matter for aiding hearing or preventing unwanted noises from entering the auditory canal.

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128Surgery,   subclasses 846+ for body protectors and restraining devices.
  
[List of Patents for class 181 subclass 130]    130Auditory canal insert:
 This subclass is indented under subclass 129.  Subject matter wherein there is a device that is operatively inserted in the auditory canal.
  
[List of Patents for class 181 subclass 131]    131Stethoscope:
 This subclass is indented under subclass 130.  Subject matter having a sensing element which is to be used in contact with a source of sound and a sound conducting element guiding the sound to an ear contacting element.

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135,for subcombination of stethoscope.

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73Measuring and Testing,   subclasses 585 , 591 and 649+, where the stethoscope is part of a testing device which tests articles or mechanisms by sensing the vibrations produced therein.
381Electrical Audio Signal Processing Systems and Devices,   subclass 67 for a stethoscope comprising a vibration-electric transducer which senses vibrations of the body by virtue of physical contact between the transducer and the body, there being no acoustical transmission through the air, and in accordance with said vibrations controls an electric current which is applied to a hearing or listening device.
  
[List of Patents for class 181 subclass 132]    132With diaphragm:
 This subclass is indented under subclass 130.  Subject matter including a flexible element which form part of a sound sensing device.
  
[List of Patents for class 181 subclass 133]    133Deflector type:
 This subclass is indented under subclass 130.  Subject matter wherein there is a device to deflect sound waves into the auditory canal.

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136,for a device to deflect sound wave to an ear where there is no element inserted into the auditory canal.
  
[List of Patents for class 181 subclass 134]    134Eardrum:
 This subclass is indented under subclass 130.  Subject matter wherein the device inserted in the auditory canal is an artificial ear drum.

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135,for ear insert only.
137,for receiver only.
  
[List of Patents for class 181 subclass 135]    135Ear insert:
 This subclass is indented under subclass 130.  Subject matter having the device inserted into the auditory canal only.
  
[List of Patents for class 181 subclass 136]    136Deflector type:
 This subclass is indented under subclass 129.  Subject matter wherein there is a device to deflect sound waves into the auditory canal.

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133,for a deflector and means to be inserted into the auditory canal.
  
[List of Patents for class 181 subclass 137]    137Receiver:
 This subclass is indented under subclass 129.  Subject matter having a sensing element only.
  
[List of Patents for class 181 subclass 138]    138MECHANICAL TELEPHONE:
 This subclass is indented under the class definition.  Subject matter wherein sound is transmitted by the vibrations of molecules set up by mechanical means in a wire, string or flexible member strung taut.

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379Telephonic Communications,   appropriate subclasses for transmission of sound by means of electrical devices.
381Electrical Audio Signal Processing Systems and Devices,   appropriate subclasses for one-way electrical transmission of audio signals.
446Amusement Devices: Toys,   subclasses 141+ for a toy telephone which is not capable for transmitting sound.
  
[List of Patents for class 181 subclass 139]    139WAVE GENERATION AND DETECTION:
 This subclass is indented under the class definition.  Subject matter for producing and receiving sonic compressional waves.
  
[List of Patents for class 181 subclass 140]    140WITH VESSEL:
 This subclass is indented under the class definition.  Subject matter for producing or receiving sonic compressional waves and a marine device.
(1) Note. This subclass includes any container for use in a water environment.
  
[List of Patents for class 181 subclass 141]    141COMBINED:
 This subclass is indented under the class definition.  Subject matter to which has been added a subcombination or assembly which is recognized as the subject matter of some other class.
  
[List of Patents for class 181 subclass 142]    142WAVE GENERATION:
 This subclass is indented under the class definition.  Subject matter for producing a sonic compressional wave.
(1) Note. A diaphragm or a diaphragm and means to move it will be placed as an original in subclasses below.

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143,for sound means and means to move the sound means.
144,for plural diaphragms.
148,for a diaphragm and enclosure.
157,for a diaphragm.
  
[List of Patents for class 181 subclass 143]    143MOVING SOUND PRODUCER OR DEFLECTOR:
 This subclass is indented under the class definition.  Subject matter for continuously moving a sound source (e.g., loudspeaker) or for continuously moving a sound reflector located in the sound path.
(1) Note. The continuous motion is generally designed to produce a tremulant effect.
  
[List of Patents for class 181 subclass 144]    144PLURAL DIAPHRAGM SOUND SOURCES:
 This subclass is indented under the class definition.  Subject matter including at least two separate means that can be vibrated by sound waves or produce sound waves.

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148,for a single diaphragm and an enclosure with plural sound emitting portions.
163,for plural dependent diaphragms.

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381Electrical Audio Signal Processing Systems and Devices,   subclasses 150+ for instruments designed to transform variable electrical current or potential into sound in combination with means to intensify the sound by mechanical means. Note especially subclasses 337+ for such combinations having sound resonators as the intensifying means. Also subclasses 193 and 202+ for diaphragm and support means with electrical means to move the diaphragm.
  
[List of Patents for class 181 subclass 145]    145Plural chambers:
 This subclass is indented under subclass 144.  Subject matter wherein the vibrated means are mounted in more than one enclosure or compartment.
(1) Note. Each enclosure or compartment may contain plural speakers.
  
[List of Patents for class 181 subclass 146]    146With sound-asborbing means:
 This subclass is indented under subclass 144.  Subject matter including sound absorbent material associated therewith for preventing undesirable effects.

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126,for sound absorbing means and an enclosure.
  
[List of Patents for class 181 subclass 147]    147Three diaphragms:
 This subclass is indented under subclass 144.  Subject matter including at least three vibrated means per unit.
  
[List of Patents for class 181 subclass 148]    148DIAPHRAGM AND ENCLOSURE:
 This subclass is indented under the class definition.  Subject matter having means that can be vibrated by sound waves or produce sound waves and means to support and means to at least partially contain the vibrated means.

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199,for a speaker enclosure, per se.

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381Electrical Audio Systems Processing Systems and Devices,   subclasses 150+ for instruments designed to transform variable electrical current or potential into sound in combination with means to intensify the sound by mechanical means. Note especially subclasses 337+ for such combinations having sound resonators as the intensifying means. Also subclass 193 and 202+ for diaphragm and support plus electrical means to move the diaphragm.
  
[List of Patents for class 181 subclass 149]    149Moisture proof:
 This subclass is indented under subclass 148.  Subject matter wherein the means to enclose the diaphragm is waterproof or rain resistant.
  
[List of Patents for class 181 subclass 150]    150Recessed (e.g., wall-mounted, etc.):
 This subclass is indented under subclass 149.  Subject matter wherein the means to support the diaphragm is provided with means to facilitate mounting within or behind a surface wall or an exposed surface.
  
[List of Patents for class 181 subclass 151]    151With sound-absorbing means:
 This subclass is indented under subclass 148.  Subject matter including sound absorbent material within the means to enclose the diaphragm for preventing undesirable effects.

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146,for plural diaphragms and sound absorbing means.
199,for an enclosure with sound absorbing means.
  
[List of Patents for class 181 subclass 152]    152With horn:
 This subclass is indented under subclass 148.  Subject matter including a tube of varying sectional area associated with the diaphragm for intensifying the sound waves produced therefrom.
  
[List of Patents for class 181 subclass 153]    153Rounded enclosure (e.g., curved, etc.):
 This subclass is indented under subclass 148.  Subject matter wherein the means to enclose the diaphragm has at least one surface that is circular or curved.
  
[List of Patents for class 181 subclass 154]    154Inclined diaphragm:
 This subclass is indented under subclass 148.  Subject matter wherein the means to support the diaphragm is mounted at an angle to both the horizontal and vertical axes of one side of the enclosure means.
  
[List of Patents for class 181 subclass 155]    155Reflector baffle:
 This subclass is indented under subclass 148.  Subject matter wherein the vibrated means is substantially enclosed and a portion of a radiation wave from in front of the vibrated means is deflected or modified.
(1) Note. The enclosure has only openings for sound to be emitted. An enclosure which has no top, back, or etc., will be found above.
  
[List of Patents for class 181 subclass 156]    156Reflex baffle:
 This subclass is indented under subclass 148.  Subject matter wherein the vibrated means is substantially enclosed and a portion of a radiation wave from the rear of the vibrated means is propagated forward after a shift or modification of the wave.
(1) Note. The enclosure has only openings for sound to be emitted. An enclosure which has no top, back or, etc., will be found above.
(2) Note. A grille of cloth or other material that sound passes through is not considered a reflector for this subclass.
  
[List of Patents for class 181 subclass 157]    157DIAPHRAGM:
 This subclass is indented under the class definition.  Subject matter including a vibratable partition which is designed to produce sound waves when driven.

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144+,for plural, independent diaphragms.
148+,for diaphragms included with an enclosure.

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381Electrical Audio Signal Processing Systems and Devices,   subclass 398 for diaphragm and electrical means to move the diaphragm.
  
[List of Patents for class 181 subclass 158]    158Microphone type:
 This subclass is indented under subclass 157.  Subject matter wherein the diaphragm is designed specifically for use in a microphone.
  
[List of Patents for class 181 subclass 159]    159With horn:
 This subclass is indented under subclass 157.  Subject matter including a sound intensifying horn acoustically coupled to the diaphragm.

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177+,for sound intensifying horns, per se.
  
[List of Patents for class 181 subclass 160]    160With resonant chamber:
 This subclass is indented under subclass 157.  Subject matter including a compartment which is acoustically coupled to the diaphragm.
(1) Note. The compartment will affect the quality, tone or loudness of the sound produced by the diaphragm.
  
[List of Patents for class 181 subclass 161]    161With direct mechanical connection to drive unit:
 This subclass is indented under subclass 157.  Subject matter including a mechanical means which directly connects the diaphragm to a driver unit.
  
[List of Patents for class 181 subclass 162]    162Stylus bar:
 This subclass is indented under subclass 161.  Subject matter wherein the driver unit is a needle or holder furnished with an abrasive-resistant tip.
(1) Note. This is primarily a collection of old style phonograph pick-up heads which include a thin metallic diaphragm directly actuated by a stylus bar.

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369Dynamic Information Storage or Retrieval,   subclasses 157 , 158, and 160+ for this subject matter forming a portion of a phonograph sound box.
  
[List of Patents for class 181 subclass 163]    163Plural dependent diaphragms:
 This subclass is indented under subclass 157.  Subject matter wherein two or more diaphragms are driven by the same mechanism, or arranged so that the sound waves produced by one cause the other to vibrate.
(1) Note. Each of the diaphragms must have at least a portion of its surface facing the surface of the other.
(2) Note. The diaphragms are usually aligned on a common axis, and may be surrounded by walls to form an airtight compartment.

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144+,for plural diaphragm sound sources which are independent from one another.
165,for a single diaphragm having more than one sound producing section.
  
[List of Patents for class 181 subclass 164]    164Sectional diaphragm:
 This subclass is indented under subclass 157.  Subject matter wherein the diaphragm has areas of different material, shape or thickness which are united to form a vibratable partition.
(1) Note. Only one independent driver unit may drive the diaphragm. When the different sections are driven independently of one another, they are considered plural, independent diaphragms and classified in subclasses 144+.
(2) Note. The different sections may have different natural periods of vibration and thus produce sound waves within different frequency ranges.

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163,for plural, dependent diaphragms.
  
[List of Patents for class 181 subclass 165]    165Concentric annular section:
 This subclass is indented under subclass 164.  Subject matter wherein the diaphragm has a central section which is attached to and surrounded by at least one concentric, annular portion.
(1) Note. The outer, ring-like section is usually designed to vibrate within a lower frequency range than the center section, and often supports the center section.

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144+,for diaphragms having sections which are independently driven, and therefore considered plural diaphragm sound sources.
163,for annular diaphragms which face another diaphragm and are driven by sound waves produced by it.
  
[List of Patents for class 181 subclass 166]    166With damping means:
 This subclass is indented under subclass 157.  Subject matter including means to suppress or limit diaphragm vibrations.
(1) Note. The damping means must be in addition to diaphragm structure, for example an air chamber, a travel limiter, or a special coating on the diaphragm.

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174,for diaphragms having portions of different thickness which might dampen vibrations.
  
[List of Patents for class 181 subclass 167]    167Critically defined material or coating:
 This subclass is indented under subclass 157.  Subject matter wherein the diaphragm is constructed of specific material or the diaphragm is covered or saturated, at least in part, with extraneous material.

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166,for diaphragm coatings specifically designed to dampen vibrations.
  
[List of Patents for class 181 subclass 168]    168Metallic material:
 This subclass is indented under subclass 167.  Subject matter wherein the material of which the diaphragm is made is metal.
  
[List of Patents for class 181 subclass 169]    169Fibrous material:
 This subclass is indented under subclass 167.  Subject matter wherein the material of which the diaphragm is made consists of or includes fibers.
  
[List of Patents for class 181 subclass 170]    170Laminated type:
 This subclass is indented under subclass 167.  Subject matter comprising plural layers or surfaces, adhered or cohered to each other.
  
[List of Patents for class 181 subclass 171]    171Mounting or suspension means:
 This subclass is indented under subclass 157.  Subject matter wherein means are provided to hold the diaphragm in a given, neutral position.
(1) Note. The mounting or suspension means may serve to shape or tension the diaphragm, or may be designed to permit the diaphragm to vibrate freely.
  
[List of Patents for class 181 subclass 172]    172Elastic suspension means:
 This subclass is indented under subclass 171.  Subject matter wherein the means to hold the diaphragm is sufficiently flexible to permit the diaphragm to vibrate freely.
  
[List of Patents for class 181 subclass 173]    173Particular shape:
 This subclass is indented under subclass 157.  Subject matter characterized by the form or configuration of the diaphragm.
  
[List of Patents for class 181 subclass 174]    174Variable thickness:
 This subclass is indented under subclass 173.  Subject matter wherein the thickness of the vibratable partition constituting the diaphragm varies across its surface.
  
[List of Patents for class 181 subclass 175]    175SOUND-MODIFYING MEANS:
 This subclass is indented under the class definition.  Subject matter for (1) deviation of the direction of an acoustical wave, (2) blocking of an acoustical wave, or (3) the modification of the character or property of an acoustical wave.
  
[List of Patents for class 181 subclass 176]    176Lens:
 This subclass is indented under subclass 175.  Subject matter wherein a structure is placed in front of an acoustic wave device having an aperture which inserts a phase delay over the cross section of the aperture so as to effect a convergence or divergence of acoustic waves from the acoustic wave device.
  
[List of Patents for class 181 subclass 177]    177Intensifying horn:
 This subclass is indented under subclass 175.  Subject matter comprising a hollow member open at opposite ends and having a progressively increasing cross sectional area from one end to the other. Sound is introduced at the smaller open end and emerges increased in loudness at the larger open end.
(1) Note. A device which both increases the loudness of the sound and modifies the quality or tone of the sound is properly classified here.

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129,for a sound intensifying horn which is designed to have contact with the human body.
152,for a horn and sound diaphragm in an enclosure.
159,for a horn and a sound producing diaphragm.
  
[List of Patents for class 181 subclass 178]    178Collapsible:
 This subclass is indented under subclass 177.  Subject matter wherein the horn includes means to effect a reduction in size from an operative condition to an inoperative condition, e.g., telescopes or folds.
  
[List of Patents for class 181 subclass 179]    179With particular mounting structure:
 This subclass is indented under subclass 177.  Subject matter including means for connecting the sound intensifying horn to a support.
(1) Note. The connecting means must be emphasized, and not merely incidental.
(2) Note. Structure which connects one portion of a horn to another portion of a horn is not considered mounting structure.
  
[List of Patents for class 181 subclass 180]    180Material:
 This subclass is indented under subclass 177.  Subject matter wherein the horn is constructed of a specific material or materials.
  
[List of Patents for class 181 subclass 181]    181With vibratory filaments:
 This subclass is indented under subclass 177.  Subject matter including thin wires which are attached to the sound intensifying horn.
(1) Note. The thin wires affect the quality or tone of the sound through vibration.
  
[List of Patents for class 181 subclass 182]    182With resonant chamber:
 This subclass is indented under subclass 177.  Subject matter including a compartment exterior to the basic horn shape, but in communication with the horn via a sound passage or a vibrating portion of the horn wall.
(1) Note. The compartment does not necessarily intensify the sound but does affect the quality or tone of the sound coming from or passing through the horn.
  
[List of Patents for class 181 subclass 183]    183Double wall:
 This subclass is indented under subclass 182.  Subject matter wherein the resonant chamber lies between at least part of a side of the horn and a second structure substantially parallel to that part of the horn.
  
[List of Patents for class 181 subclass 184]    184Having apertures in walls:
 This subclass is indented under subclass 177.  Subject matter wherein the horn has sides which are provided with openings.
(1) Note. The openings may take any shape and be covered by sound transmitting material.
(2) Note. The presence of the openings is designed to affect the quality or tone of the sound coming from or passing through the intensifying horn.

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182+,for horns having apertured walls which communicate with resonant chambers.
  
[List of Patents for class 181 subclass 185]    185With sound-path restriction:
 This subclass is indented under subclass 177.  Subject matter including structure within the horn which constitutes an obstruction to the sound waves.
(1) Note. The restriction can be an object placed within the horn or a pinch in the horn walls which generally affects the quality or tone of the sound in addition to decreasing the loudness by partially blocking the expected sound path.

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187+,for structure which merely divides the horn into plural intensifying portions.
191,for external sound deflectors.
196+,for similar structure located within a sound conveying tube.
  
[List of Patents for class 181 subclass 186]    186Adjustable:
 This subclass is indented under subclass 185.  Subject matter wherein the structure can be altered or moved within the horn.
(1) Note. Such adjustment generally affects the loudness of the sound.

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197,for similar structure within a sound conducting tube.
  
[List of Patents for class 181 subclass 187]    187Plural intensifying portions:
 This subclass is indented under subclass 177.  Subject matter wherein the sound intensifying horn comprises more than one section having an increasing cross-sectional area in the direction of travel of the sound.
(1) Note. The sections may range in type from divisions within one horn to independent horns bundled together.
  
[List of Patents for class 181 subclass 188]    188Similar portions:
 This subclass is indented under subclass 187.  Subject matter wherein the plural intensifying portions have substantially the same shape or are mirror images of one another.
  
[List of Patents for class 181 subclass 189]    189Multisection housing:
 This subclass is indented under subclass 177.  Subject matter wherein the structure forming the sound intensifying horn comprises two or more units attached together. Each unit must include part of a given sound path.

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187,for intensifying sections providing plural sound paths.
  
[List of Patents for class 181 subclass 190]    190Separable:
 This subclass is indented under subclass 189.  Subject matter wherein means are provided which permit the units to be detached from each other.
  
[List of Patents for class 181 subclass 191]    191With external sound deflector:
 This subclass is indented under subclass 177.  Subject matter including means for changing the direction of the sound after it has left the horn.
  
[List of Patents for class 181 subclass 192]    192Particular shape of the horn:
 This subclass is indented under subclass 177.  Subject matter characterized by the form or configuration of a wall of the horn.
  
[List of Patents for class 181 subclass 193]    193Spiral sound path:
 This subclass is indented under subclass 192.  Subject matter wherein the wall of the horn is arranged to provide a spiral sound path.
  
[List of Patents for class 181 subclass 194]    194Doubly folded sound path:
 This subclass is indented under subclass 192.  Subject matter wherein the wall of the horn is arranged to provide a sound path which changes direction by substantially 180 degrees at least twice.
(1) Note. Such arrangements are also called "reflex type" or "internally reversed".
  
[List of Patents for class 181 subclass 195]    195Wide angle annular outlet:
 This subclass is indented under subclass 192.  Subject matter wherein the horn has a mouth from which sound emanates and has at least a quarter circle silhouette when viewed from one of its sides.
  
[List of Patents for class 181 subclass 196]    196Within tubular means:
 This subclass is indented under subclass 175.  Subject matter wherein a mechanical restriction or valve is located within a sound conducting tubular member.
(1) Note. The structure generally affects the loudness of the sound and/or its quality or tone.

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185+,for similar structure within a sound intensifying horn.
  
[List of Patents for class 181 subclass 197]    197Adjustable:
 This subclass is indented under subclass 196.  Subject matter wherein the sound modifying structure can be altered or moved within the tubular member.

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186,for similar structure within a sound intensifying horn.
  
[List of Patents for class 181 subclass 198]    198Housing or enclosure (e.g., sound confining and absorbing):
 This subclass is indented under subclass 175.  Subject matter comprising means to at least partially contain an acoustical device.
  
[List of Patents for class 181 subclass 199]    199Speaker type:
 This subclass is indented under subclass 198.  Subject matter wherein the enclosure is for a loudspeaker.
  
[List of Patents for class 181 subclass 200]    200Machine type enclosure:
 This subclass is indented under subclass 198.  Subject matter wherein the enclosure is specially designed to confine an acoustic wave emitting device, which device does not form an element of this class type or is not claimed in combination with the subject matter of another class.
(1) Note. Subject matter of this class type in combination with or forming an element of an art device is with the appropriate art.
(2) Note. See the Index to Classification: "Anti-Noise", "Deadeners" and "Mufflers".

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352Optics: Motion Pictures,   subclass 35 for mounts and housings for motion picture apparatus with acoustical damping of the sound originating in the motion picture apparatus.
  
[List of Patents for class 181 subclass 201]    201Office type devices (e.g., typewriters, teleprinters, etc.):
 This subclass is indented under subclass 200.  Subject matter wherein the enclosure is for machines normally used and found in a business type office.
  
[List of Patents for class 181 subclass 202]    202Electrical type devices (e.g., transformers, motors, etc.):
 This subclass is indented under subclass 200.  Subject matter wherein the enclosure is for electrical apparatus.
  
[List of Patents for class 181 subclass 203]    203Reaction engine test chamber:
 This subclass is indented under subclass 200.  Subject matter wherein a reaction-type engine is completely enclosed while undergoing a testing operation.

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217,and 218, for similar devices, but which do not enclose the acoustical device.

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60Power Plants,   subclasses 200.1+ for reaction engines of this subclass type, per se.
  
[List of Patents for class 181 subclass 204]    204Internal-combustion engine:
 This subclass is indented under subclass 200.  Subject matter wherein the type of machine enclosure is for internal-combustion engines, e.g., automobiles, tractors, lawnmowers, etc.

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123Internal-Combustion Engines,   for engines of this subclass type, per se, and in combination with subject matter similar to that of this class (181), note especially subclass 198 .
  
[List of Patents for class 181 subclass 205]    205Partial enclosure or shroud:
 This subclass is indented under subclass 200.  Subject matter wherein only certain parts of a machine are enclosed, or the enclosure partially covers the device.
  
[List of Patents for class 181 subclass 206]    206By wave interference:
 This subclass is indented under subclass 175.  Subject matter wherein the means for modifying the sound includes modulating the sound by interacting or introducing an additional higher or lower frequency to the sound source, the resulting sound being at a different frequency.

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333Wave Transmission Lines and Networks,   subclasses 165+ for electrical wave filters, and particularly subclasses 186+ for electric wave filters of the electromechanical transducer type, and subclass 81 for electrical attenuators.
  
[List of Patents for class 181 subclass 207]    207Mechanical vibration attenuator:
 This subclass is indented under subclass 175.  Subject matter comprising sound deadening material physically or mechanically attached or installed on the acoustical device, or an element thereof to prevent vibratory noise usual to the operation of the device.

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73Measuring and Testing,   subclasses 514.12+ for fluid or fluent material dampening of an inertial member in an acceleration measuring apparatus and subclass 514.14 for vibration dampening in an inertial-type acceleration measuring apparatus.
105Railway Rolling Stock,   subclass 452 for sound deadeners limited thereto.
248Supports,   particularly the subclasses pertaining to resilient or vibration dampening supports for those which dampen sound.
295Railway Wheels and Axles,   subclass 7 for railway wheels having sound deadeners.
  
[List of Patents for class 181 subclass 208]    208Damping of flexural structure:
 This subclass is indented under subclass 207.  Subject matter wherein the sound deadening material is applied to vibratile structure or other bending surfaces to dampen the sound.
  
[List of Patents for class 181 subclass 209]    209Relatively moving parts:
 This subclass is indented under subclass 207.  Subject matter wherein the device has at least two parts moving with respect to one another.
  
[List of Patents for class 181 subclass 210]    210Sound absorbing fence or screen (e.g., jet engine or vehicle noise):
 This subclass is indented under subclass 175.  Subject matter comprising physical barriers which absorb, direct, and/or block sound waves from acoustical devices.
(1) Note. Subject matter of this subclass type includes, for example, sound absorbing fences erected along runways at airports and along highways.

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244Aeronautics and Astronautics,   subclass 114 for blast deflector fences arranged adjacent to runways.
  
[List of Patents for class 181 subclass 211]    211Combined:
 This subclass is indented under subclass 175.  Subject matter not provided for above comprising some acoustical device or other device having a function other than sound modifying or sound muffling combined with or in addition to sound modifying or sound muffling means.
(1) Note. Subject matter claimed in combination with or forming an element of an "Art Device" are with the appropriate art.
  
[List of Patents for class 181 subclass 212]    212Muffler, fluid conducting type:
 This subclass is indented under subclass 175.  Subject matter for conducting or guiding moving liquids or gases, and acting on such moving liquids or gases to attenuate acoustic waves therein, i.e., "mufflers".
(1) Note. Such devices in combination with or forming an element of an art device are with the appropriate art.
(2) Note. See the Index to Classification: "Anti-Noise", "Deadeners" and "Mufflers".

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60Power Plants,   subclasses 272+ and 685+ for combinations of engines or motors with means for treating the exhaust fluids.
137Fluid Handling,   appropriate subclasses for fluid handling devices not otherwise provided for.
138Pipes and Tubular Conduits,   appropriate subclasses, particularly subclasses 26+ and 37+ for related structure.
  
[List of Patents for class 181 subclass 213]    213Reaction engine type:
 This subclass is indented under subclass 212.  Subject matter comprising fluid conducting device which muffles or dampens noise emanating from a reaction type engine.
(1) Note. In the subject matter of this subclass type, the engine is usually shrouded and the muffling means are generally along the shroud.
(2) Note. For recited combinations of reaction engines and muffling means, see the reference to Class 60, Power Plants, in the Search Note below.

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60Power Plants,   for reaction engines, per se, and subclasses 272+ and 685+ for combinations of engines or motors with means for treating the exhaust fluids.
  
[List of Patents for class 181 subclass 214]    214Upstream (e.g., intake silencer):
 This subclass is indented under subclass 213.  Subject matter wherein the attenuating device is at the air intake side of the engine shroud.

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229,for internal-combustion engines having attenuating devices for the carburetor air intake.
  
[List of Patents for class 181 subclass 215]    215With adjustable outlet nozzle:
 This subclass is indented under subclass 213.  Subject matter wherein the shroud is comprised of adjustable tail end sections and the position of the shroud end sections determine the degree of attenuation.
  
[List of Patents for class 181 subclass 216]    216Longitudinally adjustable section:
 This subclass is indented under subclass 215.  Subject matter wherein the tail end sections are adjustable longitudinally of the shroud in the downstream direction.
  
[List of Patents for class 181 subclass 217]    217Removable silencer unit (e.g., mobile):
 This subclass is indented under subclass 213.  Subject matter wherein the fluid conducting device can be attached to and detached from the exhaust end of the jet engine exhaust nozzle.
(1) Note. Subject matter of this subclass type, because of its size, is usually mounted on wheels or other means for mobility.
  
[List of Patents for class 181 subclass 218]    218Ground installation silencer:
 This subclass is indented under subclass 213.  Subject matter wherein the fluid conducting device is a fixed structure with an opening to receive the tail end of a jet engine exhaust nozzle.
(1) Note. The jet engine is usually brought to the site of the structure. The structure may also be provided with multiple receiving stations.
  
[List of Patents for class 181 subclass 219]    219With adjustable internal baffles:
 This subclass is indented under subclass 213.  Subject matter wherein the jet engine shroud comprises a series of repositionable barriers spaced along the internal surface of the shroud.
  
[List of Patents for class 181 subclass 220]    220With disparate fluid mingling:
 This subclass is indented under subclass 213.  Subject matter in which a fluid is introduced into and mingled with the moving fluids to assist in muffling, as by dilution or condensing the moving fluids.
(1) Note. Chemical treatments of exhaust gases are not in this class. See Class 23, for chemical treatment.

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259+,for mufflers having fluids mixed with the exhaust for muffling the sound.

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60Power Plants,   subclasses 272+ and 685+ for combinations of engines with means for treating exhaust.
  
[List of Patents for class 181 subclass 221]    221Liquid:
 This subclass is indented under subclass 200.  Subject matter in which the added fluid is a liquid, usually water.
  
[List of Patents for class 181 subclass 222]    222With sound absorbing material:
 This subclass is indented under subclass 213.  Subject matter comprising sound absorbing material positioned in the shroud to be contacted by the exhaust gases, as by surrounding or being positioned adjacent to and communicating with the exhaust gases.

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248,252 and 256+, for similar sound absorbing devices with sound absorbing material.
  
[List of Patents for class 181 subclass 223]    223Silencer for firearms:
 This subclass is indented under subclass 212.  Subject matter comprising silencer muffler which attenuates explosive sounds generated by small firearms and which have a straight-through passage for the projectile and silencing chambers for the explosive exhaust.

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89Ordnance,   subclasses 31 and 42.01 and indented subclasses for recoil checks, flames arrestors, etc., which inherently muffle.
  
[List of Patents for class 181 subclass 224]    224Sound absorbing ventilating duct or curb (e.g., A/C, heat, air flow type):
 This subclass is indented under subclass 212.  Subject matter comprising ducts or conduits for the movement of streams of air therethrough.
(1) Note. The ducts of this subclass type are usually lined with sound absorbing material or other sound absorbing structure for attenuating the sound waves of moving air.

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454Ventilation,   subclass 262 for an air mixing building inlet airway having specific noise prohibiting structure; cross-reference art collection 906 for ventilating means, in general, including specific noise prohibiting structure; and subclasses 329, 338, and 341+ for inlet or outlet air pumps which forcefully admit or exhaust air from the stationary structure of a building.
  
[List of Patents for class 181 subclass 225]    225With fan to assist fluid flow:
 This subclass is indented under subclass 212.  Subject matter wherein there is provided rotating fan means to assist in the movement of fluid through the sound modifying means.
(1) Note. The fan of this subclass type may be operated by the force of the moving fluid or may be operated by some other mechanical means.
  
[List of Patents for class 181 subclass 226]    226With adjustable fluid flow:
 This subclass is indented under subclass 212.  Subject matter wherein there is provided some means for varying the fluid flow while attenuating and diffusing the sounds normally produced by moving fluids.
  
[List of Patents for class 181 subclass 227]    227Pipe-muffler (e.g., tail pipe type):
 This subclass is indented under subclass 212.  Subject matter wherein the fluid conducting device is comprised of a conduit with sound attenuating chambers along the length thereof.
(1) Note. Subject matter of this subclass type is generally referred to as a tail pipe, and is usually connected to a muffler which is not claimed as part of the system.
  
[List of Patents for class 181 subclass 228]    228With exhaust pipe:
 This subclass is indented under subclass 212.  Subject matter comprising an attenuating fluid conducting device in combination with an additional pipe (i.e., exhaust pipe) connected to the exhaust outlet of the attenuating device.
  
[List of Patents for class 181 subclass 229]    229Carburetor, burner, or compressor intake silencer:
 This subclass is indented under subclass 212.  Subject matter wherein the fluid conducting attenuating device is mounted on a carburetor (air intake) of an internal-combustion engine.
(1) Note. Subject matter of this subclass type includes, for example, devices designed for attenuating air intake noise for gasoline engines, compressors, and burners.
(2) Note. For structure claimed in combination with the silencer and which goes beyond the scope of this class, such as specific motor structure, or specific art device, search the appropriate art classes.

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214,for air intake silencers for jet or reaction engines.
  
[List of Patents for class 181 subclass 230]    230Pneumatic type motor (e.g., air hammer, etc.):
 This subclass is indented under subclass 212.  Subject matter wherein the fluid conducting attenuating device is mounted on the exhaust end of a compressed air or vacuum actuated motor (i.e., air hammer, tool, etc.).
(1) Note. Structure claimed in combination with the silencer and which goes beyond the scope of the class is classified with the art device. For example, the combination of an impact tool plus a muffler for the tool is classified with the impact tool.

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173Tool Driving or Impacting,   appropriate subclasses for pneumatic tools, and specifically Digest 2 for sound muffling.
415Rotary Kinetic Fluid Motors or Pumps,   subclass 119 for sound or vibratory wave absorbing or preventing means.
  
[List of Patents for class 181 subclass 231]    231With solid particle separator (e.g., spark arrestor, vacuum cleaner, etc.):
 This subclass is indented under subclass 212.  Subject matter wherein there is provided additional means which at the same time remove from the moving fluids (exhaust) all entrained dirt particles, sparks, and the like.

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96Gas Separation: Apparatus,   subclasses 380+ for gas separation apparatus having sound damping means.
  
[List of Patents for class 181 subclass 232]    232Separate distinct units serially connected:
 This subclass is indented under subclass 212.  Subject matter provided with a plurality of sound attenuating devices, each either of duplicate or different design and connected one after the other in the down-stream direction.
  
[List of Patents for class 181 subclass 233]    233Liquid motion silencer:
 This subclass is indented under subclass 212.  Subject matter wherein the fluid conducting attenuating device suppresses the transmission of sound waves or similar vibrations (fluid impulses) along pipes and conduits carrying fluids.

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227,for pipe mufflers for handling exhaust gases.

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138Pipes and Tubular Conduits,   appropriate subclasses, particularly subclasses 26+ and 37+ for related structure.
  
[List of Patents for class 181 subclass 234]    234Water-closet type:
 This subclass is indented under subclass 233.  Subject matter in which the fluid conductor is part of a fluid supply leading to or part of a water closet.

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4Baths, Closets, Sinks, and Spittoons,   appropriate subclasses for water closets, per se.
  
[List of Patents for class 181 subclass 235]    235Underwater discharge:
 This subclass is indented under subclass 212.  Subject matter wherein the fluid is ejected under water.
  
[List of Patents for class 181 subclass 236]    236With muffler cut-out:
 This subclass is indented under subclass 212.  Subject matter comprising a valve device which can be utilized for diverting the moving fluid away from the fluid conducting attenuating device which performs the muffling operation.
  
[List of Patents for class 181 subclass 237]    237With pressure relief safety valve:
 This subclass is indented under subclass 212.  Subject matter wherein there is provided a valve responsive to relieve excess pressure to the atmosphere.

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137Fluid Handling,   subclasses 455+ for valves responsive to change in line condition.
  
[List of Patents for class 181 subclass 238]    238Multiple distinct inlets and/or outlets:
 This subclass is indented under subclass 212.  Subject matter wherein the moving fluid is introduced in the muffler via at least two inlets or expelled through at least two outlets.
  
[List of Patents for class 181 subclass 239]    239Outlets:
 This subclass is indented under subclass 238.  Subject matter comprising a plurality of fluid outlets or discharge ports.
  
[List of Patents for class 181 subclass 240]    240Manifold type:
 This subclass is indented under subclass 212.  Subject matter for collecting and conducting the fluids from single or multiple cylinders into a single exhaust pipe.
  
[List of Patents for class 181 subclass 241]    241Adjustable muffler (i.e., internal or external parts):
 This subclass is indented under subclass 212.  Subject matter wherein two or more of the internal parts of external casing sections can be repositioned relative to each other to change the size of the muffler.
  
[List of Patents for class 181 subclass 242]    242Mouthpieces (e.g., telephone, microphone, etc.):
 This subclass is indented under subclass 212.  Subject matter comprising devices constructed to be spoken into.
(1) Note. Only such parts of the device necessary to establish the environment are included in this subclass. For devices such as microphones, telephones, etc., per se, search the appropriate art.

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379Telephonic Communications,   subclasses 437+ for such devices in combination with telephones.
  
[List of Patents for class 181 subclass 243]    243With repair, replacement, or quick disassembly:
 This subclass is indented under subclass 212.  Subject matter having means to facilitate the repair of damaged parts or elements of the muffling device.
(1) Note. Subject matter of this subclass type includes, for example, muffling devices which can be disassembled with minimum mechanical manipulations.
  
[List of Patents for class 181 subclass 244]    244Corrosion prevention:
 This subclass is indented under subclass 212.  Subject matter comprising means for preventing chemical erosion of the material of which the device is made.
  
[List of Patents for class 181 subclass 245]    245Internally coated parts:
 This subclass is indented under subclass 244.  Subject matter wherein at least some of the fluid contacting surfaces of the conducting devices are coated so as to prevent corrosion.
  
[List of Patents for class 181 subclass 246]    246Nonmetallic:
 This subclass is indented under subclass 244.  Subject matter wherein the fluid conducting device is constructed of organic materials.
  
[List of Patents for class 181 subclass 247]    247Straight-through passage:
 This subclass is indented under subclass 212.  Subject matter wherein the fluid is conducted through a fluid conducting device having a linear, unobstructed passage at least the same size from the inlet to the outlet.
  
[List of Patents for class 181 subclass 248]    248Continuous conduit:
 This subclass is indented under subclass 247.  Subject matter wherein the passage is comprised of a continuous uninterrupted conduit from its inlet to the outlet.
(1) Note. Subject matter of this subclass type may have sound absorbing material.

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222,252 and 256, for similar sound absorbing devices with sound absorbing material.
  
[List of Patents for class 181 subclass 249]    249With expansion chamber:
 This subclass is indented under subclass 248.  Subject matter having enlarged chambers intermediate the length of the through passage.
  
[List of Patents for class 181 subclass 250]    250And side branch:
 This subclass is indented under subclass 249.  Subject matter having cushion, acoustic filter, or resonator chambers in communication with the through passage.

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266,273 and 276, for similar devices with side branch chamber.
  
[List of Patents for class 181 subclass 251]    251And multipassage:
 This subclass is indented under subclass 249.  Subject matter having a plurality of through passages between which the moving fluid is divided.
  
[List of Patents for class 181 subclass 252]    252With sound absorbing material:
 This subclass is indented under subclass 247.  Subject matter having acoustic wave attenuating material positioned within the fluid conducting device to be contacted by the exhaust fluid as by surrounding the through passage or being positioned adjacent to and communicating with the exhaust fluids.

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222,248 and 256, for similar sound absorbing devices having sound absorbing material.
  
[List of Patents for class 181 subclass 253]    253With muffler bypass:
 This subclass is indented under subclass 247.  Subject matter having one or more passages, which performs a muffling function, which bypass the whole or part of the through passage.
(1) Note. Subject matter of this subclass type includes, for example, devices in which the bypassed fluid is returned out of phase with the fluid in the through passage.

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236,in which the fluids are diverted from the muffler and are not muffled.
268,for devices which have a plurality of through passages connected in parallel.
  
[List of Patents for class 181 subclass 254]    254Valve controlled:
 This subclass is indented under subclass 253.  Subject matter having means to vary the rate of fluid flow in either the through or the bypass passage.
  
[List of Patents for class 181 subclass 255]    255Expansion chamber:
 This subclass is indented under subclass 247.  Subject matter having enlarged chambers intermediate the length of the through passage.
  
[List of Patents for class 181 subclass 256]    256With Sound absorbing material:
 This subclass is indented under subclass 212.  Subject matter having acoustic wave attenuating material positioned to be contacted by the moving fluid, as by surrounding or being positioned adjacent to and communicating with the fluid passage.

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222,for jet engine muffler devices having sound absorbing material.
247,for straight-through continuous passage mufflers having sound absorbing material.
252,for through passage mufflers with sound absorbing material.
  
[List of Patents for class 181 subclass 257]    257And multipassage:
 This subclass is indented under subclass 256.  Subject matter having a plurality of passages between which the moving fluid is divided.
  
[List of Patents for class 181 subclass 258]    258Pervious material interposed in flow path:
 This subclass is indented under subclass 256.  Subject matter wherein the sound absorbing material is directly in the flow path of the moving fluid, and the fluid must pass through the material to its exit.
  
[List of Patents for class 181 subclass 259]    259With disparate fluid mingling:
 This subclass is indented under subclass 212.  Subject matter in which a fluid is introduced into and mingled with the moving fluids to assist in muffling, as by diluting and condensing the moving fluids.

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220+,for similar devices in jet engines.
  
[List of Patents for class 181 subclass 260]    260Liquid:
 This subclass is indented under subclass 259.  Subject matter in which the added fluid is a liquid, usually water.
  
[List of Patents for class 181 subclass 261]    261Sprayed:
 This subclass is indented under subclass 260.  Subject matter in which the liquid is injected into the main stream of exhaust by some diffusing means.
  
[List of Patents for class 181 subclass 262]    262Induced by suction:
 This subclass is indented under subclass 259.  Subject matter wherein the device is provided with openings for admitting the fluid through said opening as a result of a vacuum created by the moving exhaust fluids.
  
[List of Patents for class 181 subclass 263]    263Motion induced:
 This subclass is indented under subclass 262.  Subject matter wherein the motion of the device on which the muffler is installed creates a vacuum by scooping a fluid as the device moves.
  
[List of Patents for class 181 subclass 264]    264With baffle or baffle structure:
 This subclass is indented under subclass 212.  Subject matter in which barriers or partitions cause the fluids to travel in a tortuous path.
  
[List of Patents for class 181 subclass 265]    265Retroverted:
 This subclass is indented under subclass 264.  Subject matter having a plurality of serially connected fluid passages substantially parallel to the inlet, the direction of flow of the fluid being reversed as it travels through each successive passage.
  
[List of Patents for class 181 subclass 266]    266And side branch chamber:
 This subclass is indented under subclass 265.  Subject matter having cushion, acoustic filter, or resonator chambers in communication with the fluid passage.

SEE OR SEARCH THIS CLASS, SUBCLASS:

250,and 273, for similar devices with side branch chambers.
  
[List of Patents for class 181 subclass 267]    267Coaxial foraminous walls:
 This subclass is indented under subclass 264.  Subject matter in which are provided a plurality of coaxial cylindrical chambers having fluid pervious walls through which the fluid flows in a radial direction into the atmosphere.
  
[List of Patents for class 181 subclass 268]    268Multipassage:
 This subclass is indented under subclass 264.  Subject matter having a plurality of passages between which the moving fluid is divided.
  
[List of Patents for class 181 subclass 269]    269Expansion chamber type:
 This subclass is indented under subclass 264.  Subject matter having an enlarged chamber intermediate the length of the fluid passage.
  
[List of Patents for class 181 subclass 270]    270With alternating partial baffles along the length of casing:
 This subclass is indented under subclass 269.  Subject matter wherein there is a plurality of partial barriers alternately spaced along the length of the muffler casing.
  
[List of Patents for class 181 subclass 271]    271With adjustable or flexible wall:
 This subclass is indented under subclass 269.  Subject matter wherein at least one of the partitions defining the chamber is repositionable with respect to another.
  
[List of Patents for class 181 subclass 272]    272Plural chambers:
 This subclass is indented under subclass 269.  Subject matter having more than one expansion chamber.
  
[List of Patents for class 181 subclass 273]    273And side branch chamber:
 This subclass is indented under subclass 269.  Subject matter having cushion, acoustic filter, or resonator chambers in communication with the fluid passages.

SEE OR SEARCH THIS CLASS, SUBCLASS:

250,266 and 276, for similar devices with side branch chambers.
  
[List of Patents for class 181 subclass 274]    274With centrifugal flow:
 This subclass is indented under subclass 269.  Subject matter in which the inlet to the expansion chamber and the baffles are in such direction as to impel the fluid into a circular flow.
  
[List of Patents for class 181 subclass 275]    275And multipassage:
 This subclass is indented under subclass 269.  Subject matter having a plurality of passages between which the moving fluid is divided.
  
[List of Patents for class 181 subclass 276]    276Side branch:
 This subclass is indented under subclass 264.  Subject matter having cushion, acoustic filter, or resonator chambers in communication with the fluid passages.
  
[List of Patents for class 181 subclass 277]    277Movable baffle:
 This subclass is indented under subclass 264.  Subject matter having baffles constantly in motion, and driven either under the force of the moving fluid or by some external means.
(1) Note. Subject matter of this subclass type includes, for example, baffles which form rotating vanes.
  
[List of Patents for class 181 subclass 278]    278Biased:
 This subclass is indented under subclass 277.  Subject matter having means tending to force the moving baffle toward a position to restrict flow of fluid.
  
[List of Patents for class 181 subclass 279]    279Spiral:
 This subclass is indented under subclass 264.  Subject matter in which the baffles are arranged to guide the moving fluid through an axially or radially expanding, circular path.
  
[List of Patents for class 181 subclass 280]    280Helical:
 This subclass is indented under subclass 279.  Subject matter in which the circular path is axially expanding.
  
[List of Patents for class 181 subclass 281]    281Perpendicular and/or oblique:
 This subclass is indented under subclass 264.  Subject matter having baffles angularly disposed relative to the axis of the flow passage, i.e., not parallel to the axis.
  
[List of Patents for class 181 subclass 282]    282Casings:
 This subclass is indented under subclass 264.  Subject matter comprising the jacket or housing structure of the fluid handling device wherein the jacket or housing structure is more than nominally recited.

SEE OR SEARCH CLASS:

165Heat Exchange,   subclasses 52 , 154, or 157 for casings with a surrounding jacket to form a space for circulating cooling fluids.
  
[List of Patents for class 181 subclass 283]    283Air or liquid cooled:
 This subclass is indented under subclass 282.  Subject matter having a chamber or other structure for providing a cooling fluid to lower the temperature of the moving exhaust fluids.
  
[List of Patents for class 181 subclass 284]    284Sound absorbing panels:
 This subclass is indented under subclass 175.  Subject matter comprising planar-type structure for attenuating acoustic waves.

SEE OR SEARCH CLASS:

52Static Structures (e.g., Buildings),   subclasses 144+ for a combination of units having an exposed surface configuration having an acoustical function, or a unit with a feature for such a combination.
428Stock Material or Miscellaneous Articles,   for a product or stock material.
  
[List of Patents for class 181 subclass 285]    285Load bearing block type structure:
 This subclass is indented under subclass 284.  Subject matter comprising sound attenuating structural elements or units, e.g., blocks, sufficiently strong or rigid to support a load.

SEE OR SEARCH CLASS:

52Static Structures (e.g., Buildings),   subclasses 144+ for a combination of units having an exposed surface configuration having an acoustical function, or a unit with a feature for such a combination.
  
[List of Patents for class 181 subclass 286]    286Specific acoustical properties or dimensions:
 This subclass is indented under subclass 284.  Subject matter whose composition, size or shape is related to a particular type of acoustic wave attenuation, e.g., insertion loss, transmission loss, or specific acoustic structure (Helmholtz resonator, 1/4 wavelength chamber depth).
  
[List of Patents for class 181 subclass 287]    287Movable/foldable panels:
 This subclass is indented under subclass 284.  Subject matter specifically designed to be flexible, hinged, or portable.
(1) Note. Subject matter of this subclass type includes, for example, curtain or drape-like products.

SEE OR SEARCH CLASS:

49Movable or Removable Closures,   appropriate subclass for such devices.
160Flexible or Portable Closure, Partition, or Panel,   appropriate subclass for such devices.
  
[List of Patents for class 181 subclass 288]    288Cellular:
 This subclass is indented under subclass 284.  Subject matter comprising either discrete elements (e.g., tubular constituents) or components which form, or cooperate to form, cavities the longitudinal axis of which are at an angle to the plane of the major face of the product.
(1) Note. Multilayer products having one layer formed as a honeycomb-like or cellular layer are found in this class, subclasses 290+.
  
[List of Patents for class 181 subclass 289]    289Light permeable:
 This subclass is indented under subclass 284.  Subject matter which is translucent or transparent to visible radiation.
  
[List of Patents for class 181 subclass 290]    290Multilayer panel or wall structure:
 This subclass is indented under subclass 284.  Subject matter comprising more than one layer of sound attenuating material.
  
[List of Patents for class 181 subclass 291]    291With membrane outer layer:
 This subclass is indented under subclass 290.  Subject matter having a front or rear facing formed as a coating, foil, or film.
  
[List of Patents for class 181 subclass 292]    292With perforated or porous face and honeycomb-like core:
 This subclass is indented under subclass 290.  Subject matter having at least one porous or perforated layer and at least one honeycomb-like layer.
(1) Note. Typically, such products are used as reaction engine duct liners.
  
[List of Patents for class 181 subclass 293]    293With channels or cavities in surface layer:
 This subclass is indented under subclass 284.  Subject matter wherein the outer face is formed with channels or cavities.
  
[List of Patents for class 181 subclass 294]    294Materials:
 This subclass is indented under subclass 284.  Subject matter characterized by the particular sound absorbing material used to form the product.

SEE OR SEARCH CLASS:

106Compositions: Coating or Plastic,   for such compositions which have sound deadening properties.
252Compositions,   subclass 62 for heat or sound insulating compositions.
428Stock Material or Miscellaneous Articles,   subclasses 411.1+ for laminate characterized by compositions of laminas.
  
[List of Patents for class 181 subclass 295]    295Space absorber:
 This subclass is indented under subclass 175.  Subject matter comprising structures of sound absorbing material for absorbing acoustic energy in rooms or similar chambers within which the structure is enclosed.
(1) Note. Subject matter of this subclass type, for example, is usually formed as a hollow box and suspended from a wall or ceiling or used in anechoic chambers.
  
[List of Patents for class 181 subclass 296]    296Methods:
 This subclass is indented under subclass 175.  Subject matter comprising methods of attenuating sound.
(1) Note. Methods of this subclass type may attenuate the entire sound or selected frequencies thereof.
(2) Note. Patents claiming both a method of attenuating sound and a product or apparatus for attenuating sound are placed above in the appropriate subclass and cross-referenced here.
(3) Note. Methods of making a sound attenuating product or apparatus are found in the various manufacturing classes involved.
  

CROSS-REFERENCE ART COLLECTIONS

The following subclasses are collections of published disclosures pertaining to various specified aspects of the acoustic art which aspects do not form appropriate bases for subclasses in the foregoing classification (i.e., subclasses superior hereto in the schedule), wherein original copies of patents are placed on the basis of proximate function of the apparatus. These subclasses assist a search based on remote function of the apparatus and may be of further assistance to the searcher, either as a starting point in further related fields of search inside or outside the class. Thus, there is here provided a second access for retrieval of a limited number of types of disclosure.

(1) Note. Disclosures are placed in these subclasses for their value as references and as leads to appropriate main or secondary fields of search, without regard to their original classification of their claimed subject matter.
(2) Note. The disclosures found in the following subclasses are examples, only of the indicated subject matter, and in no instance do they represent the entire extent of the prior art.
(3) Note. Original copies of patents are not placed in the following subclasses.
[List of Patents for class 181 subclass 400]    400
 Elements or material for transforming sound wave energy from high to low pressure and vice versa.
(1) Note. Included herein are means to transmit sound waves from one medium to another medium with minimum reflection, deviation or absorption wherein the means acts as a mechanical impedance matching means. The impedance matching may be a function of the material or may be due to the shape or configuration of an element such as a horn shape.

SEE OR SEARCH THIS CLASS, SUBCLASS:

175+,for material or elements for attenuating sound waves.
  
[List of Patents for class 181 subclass 401]    401
 This subclass is indented under subclass 400.  Elements or material wherein one of the media is the earth.
  
[List of Patents for class 181 subclass 402]    402
 This subclass is indented under subclass 400.  Elements or material wherein one of the media is a liquid.
  
[List of Patents for class 181 subclass 403]    403REFRIGERATOR COMPRESSOR MUF­FLER:
 Disclosures of sound attenuating mufflers for refrigerator compressors.

SEE OR SEARCH CLASS:

417Pumps,   subclass 312 for pumps with mufflers acting on the pumped fluid.
  
[List of Patents for class 181 subclass 404]    404HOBBY CRAFT ENGINE MUFFLER:
 Disclosures of toy engines or hobby craft-type engines with sound attenuating mufflers.
  

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