Devices that produce a sound by striking a resonating body, such as bells, chimes, gong.

Whistles, siren devices that produce a sound driven by rotating member, motor, or fluids, e.g., compressed gas.

Devices that produce a sound by vibrating a diaphragm or analogous element, such as foghorns, vehicle hooter, buzzer.

Methods or devices that transmit, conduct, or direct a sound wave.

Methods or devices for protection against, or damping of, acoustic waves.

Cones, diaphragms, or the like, for emitting or receiving sound.

Acoustics not otherwise provided for.

Arrangements for generating mechanical vibrations in fluids.

The production of sounds which may not be audible to human beings but which are audible to animals.

When classifying in subgroups G10K 9/122-G10K 9/22, the subgroups do not cover the construction of, or circuits for, broadband-transducers, such as loudspeakers or microphones, which are covered by subclass H04R.

When classifying in subgroups G10K 11/162-G10K 11/168, the subgroups do not cover protecting against, or damping of, acoustic waves adapted for particular applications, which are covered by the subclasses for these applications, provided that there is a specific provision for this aspect.

When classifying in subgroups G10K 11/16-G10K 11/172, classification is also made in subclass B32B, in so far as any layered product is concerned.

For details which are not covered by specific subgroups of G10K, the Indexing Codes G10K 2200/00 and G10K 2200/00 should be applied.

Door-knockers

Infrasonic, sonic, and ultrasonic whistles

Sirens where the sound is created by chopping a flow of air

Methods or devices that transmit, conduct, or direct a sound wave.

Methods or devices for protection against, or damping of, acoustic waves.

Methods or devices for damping acoustic waves by electroacoustically regenerating the original acoustic waves in antiphase, and superimposing the two acoustic waves

Diffusers (G10K 11/20)

Damping or steering of surface acoustic waves

The subgroups G10K 11/162-G10K 11/168 cover the selection of materials for the devices for protecting against, or damping of, acoustic waves. Subject-matter, which normally would be covered by these groups, which is adapted for particular applications, which are covered by the classes for these applications, is to be classified with those applications provided that there is a specific provision for the aspect of protecting against, or damping of, acoustic waves.

When classifying in subgroups G10K 11/16-G10K 11/172, classification is also to be made in subclass B32B, in so far as any layered product is concerned.

Devices for damping, suppressing, obstructing or conducting sound in acoustic devices, e.g. for preventing cavitation in acoustic devices

Sound absorbers where the matrix is a gas and where the particles are in a fixed position

Acoustic active noise cancellation [ANC], i.e. issuing an acoustic wave field that destructively interferes with a pre-existing acoustic wave field, for the purposes of reducing or damping the pre-existing acoustic wave field.

The scheme has 4 main branches:

The analysis of input signals, output signals, or relationships between them, which are used by the invention in a special way to achieve its goal is classified in G10K 11/1781. For instance, if an application analyses a musical signal and turns off ANC if the music is very loud, G10K 11/17827 should be assigned.

The handling of specific non-standard conditions, e.g. detection of instabilities or other malfunctions in the device, or detection of specific signals that must not be cancelled, e.g. speech, sirens or warnings, is classified in G10K 11/1783.

Inventions about specific details, e.g. specific details of the adaptive filter, hardware or software implementations for lowering power requirements or improving speed, geometric placement of loudspeakers and microphones or combinations with other acoustic elements, are classified in G10K 11/1785.

The overall ANC circuit structure is classified in G10K 11/1787, with the idea of having similar circuits together in one group. For instance, ANC in cars often involves a synthesizer using a reference signal based on engine parameters; as another example, systems in which music is to be played together with the ANC signal mostly have sub circuits that estimate and subtract the music signal from the error signal before the error signal is used to adapt the ANC signal.

This group is a "function-oriented place" for acoustic active noise cancellation and covers active cancellation of acoustic noise by physical mixing of the pre-existing acoustic noise wave field with the generated acoustic wave field.

Noise cancellation in electronic or electroacoustic signals by mixing, processing or otherwise altering the signal inside the circuitry is classified elsewhere, even though the methods used might often be similar. For example, a phone cancelling or reducing noise that is part of a signal coming from a telephone network, e.g. line noise or echo noise, by filtering this signal, is not seen as acoustic noise cancellation within the scope of G10K 11/178, but falls within the scope of H04M.

However, the mere application of ANC in telephones, e.g. a phone reducing or cancelling ambient noise around the user, by mixing an acoustic anti-noise signal into the signal coming from the network, to destructively interfere with the ambient acoustic noise, is seen as applying acoustic noise cancellation within the scope of G10K 11/178.

Classification in several subgroups is specifically encouraged in this scheme, especially in the general system configurations subgroup. For instance, a phone general device with active acoustic noise cancellation comprising a diagnostics function, and using a reference microphone, an error microphone and a desired music signal is classified under G10K 11/17833, G10K 11/17879 and G10K 11/17885.

When classifying in G10K 11/178, classifying additional information in the subgroups of G10K 2210/00 is mandatory.

Background

In acoustic anti-noise systems, an acoustic transducer (e.g. loudspeaker) generates an acoustic signal to compensate for an existing ambient noise signal, such that the total acoustic signal at a specific point or area (the so called "quiet zone") is minimized, by generating the noise signal in anti-phase.

To achieve this goal, a number of different input signals can be used:

In essence, the basic ANC system of Figure 1 predicts the noise in front of the loudspeaker from signal x(n), by taking into account a time delay and acoustic distortions, and outputs it in anti-phase through the loudspeaker. Ideally, this completely cancels the noise. The input e(n) is used to fine-tune the system, by adapting the ANC filtering such that e(n) is minimized.

Figure 1. Combined feedforward and feedback ANC in a duct.

It is possible to do ANC with only a reference signal, only an error signal or with both reference and error signals. The desired external signal is an optional extension of the ANC system. ANC with only a reference signal (i.e. without an error signal) is called pure feedforward ANC.

The acoustic path from the reference microphone to the error microphone is referred to here as the primary path, often denoted by P(z). Feedforward (and hybrid) ANC systems usually model this path to predict the noise at the error microphone from the detected reference signal.

The electro-acoustic path through the loudspeaker to the error microphone is referred to here as the secondary path, often denoted by S(z). Feedback (and hybrid) ANC systems model this path to compensate for non-linear effects of the loudspeaker and error microphone and the specific acoustic environment between the two. Also, this path is modelled to be able to remove the desired external signal from the measured error signal.

The electro-acoustic path through the loudspeaker to the reference microphone is sometimes referred to as the leakage path. This path is modelled to be able to remove the anti-noise signal itself from the measured reference signal, e.g. to prevent howling. Also, this path can be modelled to compensate for non-linear effects of the loudspeaker and reference microphone and the specific acoustic environment between the two.

Basic adaptive control is often performed using a combined model W(z) = -P(z) / S(z), which is multiplied by the secondary path, S(z), to arrive at a signal approximating the true P(z). See Figure 2.

Figure 2. Adaptive feedforward ANC.

Often, the secondary path is also adaptively modelled to adapt to changes in the acoustic environment, such as movement of a telephone or head-phone with respect to the user's head.

The coupling through acoustic paths from the loudspeaker to the reference microphone is normally be kept as low as possible, so as to prevent howling (i.e. the ANC system detecting its own output as noise and worsening it). Confusingly, the word "feedback" is sometimes used for this coupling, in reference to the effect in musical performances.

Diffusers

Diffraction

Damping, steering of Surface Acoustic Waves

Synthesis of acoustic waves

Sound-producing devices not otherwise provided for

Arrangements for producing a reverberation sound

Acoustic levitation

Matter transportation using acoustic waves

Modulation, parametric techniques

SASERS

Unipolar generators