Signal processing or circuitry for two or more channel sound reproduction, using loudspeakers or headphones, or for two or more channel sound capture, using microphones.

Concerning G10L 19/008, this group covers in principle coding, processing in the coded state, and decoding of stereophonic audio signals for redundancy reduction, whereas processing of stereophonic audio signals in the decoded stated, i.e. before coding (e.g. sound capturing) or after decoding (e.g. sound rendering) is covered by H04S.

Electronic sound processing in two-channel systems wherein the processing itself is independent on the input signal or its properties.

Multi-channel, i.e. more than two input channels, sound reproduction with two speakers wherein the multi-channel information is substantially preserved is not to be classified under H04S 1/00 but under H04S 3/00, H04S 5/00 or H04S 7/00 using the Indexing Code H04S 2400/01.

Classification is obligatory.

Electronic sound processing for enhancing the sound image or the spatial distribution, wherein the processing itself is static or manually adjustable (e.g. Figure below).

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Electronic sound processing in systems employing more than two channels wherein the processing itself is independent on the input signal or its properties.

Further detail is covered by Indexing Code groups H04R 2203/12, H04S 2400/01, H04S 2400/03, H04S 2400/05, H04S 2420/11 and H04S 2420/13. Classification is obligatory.

Electronic sound processing for enhancing the sound image or the spatial distribution, wherein the processing itself is static or manually adjustable (e.g. Figure below).

Spatial sound processing employing more than two discrete digital channels.

Using a matrix arrangement that routes multiple input audio signals to multiple outputs.

Typical example:

Systems wherein one or more additional channels are generated from one or more of the existing channels to improve the spatial sound reproduction, e.g. wave field synthesis or virtual surround sound, or the spatial sound capture, e.g. 4-channel ambisonic capture to 7.1-channel.

Further detail is covered by Indexing Code groups H04R 2203/12, H04S 2400/01, H04S 2400/03, H04S 2400/05, H04S 2420/11, and H04S 2420/13.

Classification is obligatory.

Systems wherein more than four additional channels are generated from the existing channels. Example for sound reproduction with two channel stereophonic source signal reproduced over five loudspeaker channels.

Example for sound capture with input three microphone channels, output five loudspeaker channels, see figure below:

Further detail is covered by Indexing Code groups H04R 2203/12, H04S 2400/01, H04S 2400/03, H04S 2400/05, H04S 2400/07, H04S 2400/11, H04S 2400/13 and H04S 2420/13.

Classification is obligatory.

Electronic sound processing adaptable in dependence of

Example for adaptation of the sound field (e.g. shading effects) in dependence of the number and position of passengers in the vehicle. Directionally deviations due to shading is measured. Once measured the sound field is adapted accordingly (see figure).

Automatic set-up. In the example below calibration is carried out with respect to the relative gains in the listener position by using a test microphone and a noise generator.

In the example below calibration is carried out with respect to the signal delays in the listener position (12) by a determining the distance between the remote control (14,16) and each loudspeaker using low frequency pulses sent by the control and received by pulse counter (22a-22e) provided with each speaker (20a-20e).

Aspects of adaptation of a sound system with respect to listener position (see figures) or orientation relative to the loudspeakers or virtual sound sources. The calibration can be automatic.

System in which the listener position or orientation (P) is tracked, e.g. with a camera (26a, 26b) (see Figure) and the sound field is adapted accordingly.

System adapted for headphones (61) in which the orientation of the listener head is tracked, e.g. with a rotation angle sensor (71) and the sound delivered to the headphone (6R, 6L) is adapted accordingly (see figure).

Reverberation adaption to the sound field. Example for adaptation of reverberation in a room (see figure).

Example for adaptation of reverberation in dependence of the number and position of passengers (A,B,C,D) in the vehicle (201). Variations in reverberation due to the passengers are measured. Once measured, reverberation is adapted accordingly (see figure).

Frequency adaption to the sound field. Example for adaptation of frequency in dependence of the number and position of passengers in the vehicle. Variations in frequency due to the passengers are measured. Once measured, the frequency response is adapted accordingly (see figure).

Adaptation of the stereophonic signal processing in dependence of the state of electrical connection of loudspeakers/headphones to respective output channels of stereophonic amplifiers.

For example, a multichannel system wherein the low frequency signals are treated differently depending on the presence of a subwoofer (see figure).

For example, a multi-room system with different loudspeaker configuration in the respective sound zones (see figure (Z1-Z4)). Audio signal processing of the multichannel sound signal is depending on the zone (room) the sound signal is outputted to.

Display showing stereophonic sound image. For example, indicating power and the frequency of the channels (X1-X5) as shown in the figure. The shading indicates the frequency characteristics and the radius of the shaded area the power of the signal for the channels.

Channels are displayed and by sliding one of the controls one can rotate, change the width and the amplitude of the source channels which is visualised in the display.

Preservation of the multi-channel information is essential when reducing the number (more than two) of channels to two.

For example:

NOT to be given for H04S 1/00 since no multi-channel sound information is present according to H04S 1/00.

The multi-channel information should be preserved as much as possible when reducing the number (more than two) of channels.

For example a reduction from five input channels to four.

The mere presence of downward compatibility is not to be classified.

Signal processing with respect to the centre channel, e.g. generation, redistribution or adaptation.

Example for adaptation of centre channel (S):

Signal processing with respect to the LFE channel, e.g. generation, redistribution. Figure 1. Example for of LFE channel of a 5.1 system to the other five channel (5.0 system).

Figure 2. Example of redistribution of low frequency components of the 5 channels of a 5.1 system to the LFE channel.

Distortion can be caused by the reproduction components (speakers, signal processing). In the example below the phase distortion is reduced.

Distortion can be due to standing waves, which are in the example below suppressed by compensating loudspeaker 5.

Figure 1. Sound objects are first extracted during recording and combined reproduction.

Figure 2. Extraction can be done with the help of a camera.

Control of volume.

Figure 1. Volume Control

For example, note the following figure showing aspects of volume control.

Figure 1. Capture and reproduction of sound objects.

Figure 2. Capture and reproduction of sound field.

Documents only relating to spatial or constructional arrangements of microphones should not receive this Indexing Code group.

Improvement of the sound field taking transfer functions between ears and sound sources into account.

Examples:

Figure 1. 2-channel stereophonic reproduction on binaural headphones.

Figure 2. 5.1 reproduction on binaural headphones.

Figure 3. using HRTF to improve localisation for a binaural hearing aid system.

Aspects regarding parametric coding affecting the rendering in a stereophonic audio system.

For example:

Reduced computational load due to frequency dependent Binaural Cue Coding (BCC) analysis and synthesis.

The use of the Haas effect to control the sound localisation from loudspeakers in a stereophonic sound sytem.

For example in the figure below: low frequency components of the centre output signal is routed to the main loudspeakers and is thus heard if coming from small centre channel loudspeaker.

For example: Improved pseudo stereo generation by splitting the mono signal in different frequency bands (H₁(z), H₂(z)) and applying for band a different type of pseudo-stereo splitting filter (H₁₁(z), H₁₂(z), H₂₁(z), H₂₂(z); e.g. according to H. Lauridsen). Thus, the high frequency contribution to the pseudo stereo can be improved.

The mere indication of band splitting or presence of a filter bank (e.g. fast Fourier transform (FFT); or finite impulse response (FIR)) is not sufficient to mandate classification into this Indexing Code group.

The ambisonic B-format system is a high quality sound positioning system which operates by breaking down the directionality of the sound into spherical harmonic components termed W, X, Y and Z

For example:

Figure 1.

Figure 2.

Wave-field synthesis is a spatial audio rendering technique based on the Huygens–Fresnel principle, which states that any wave front can be regarded as a superposition of elementary spherical waves.

For example: