Device and method for tuning a frequency-dependent attenuation stage

Patent metadata

Field	Value
Publication number	US-10283137-B2
Application number	US-201515119687-A
Country	US
Kind code	B2
Filing date	Feb 18, 2015
Priority date	Feb 18, 2014
Publication date	May 7, 2019
Grant date	May 7, 2019

Abstract

A device (160) and a method are proposed for tuning a frequency-dependent attenuation stage (122), with the purpose of suppressing non-linear distortion occurring in an audio reproduction system (120) associated with the frequency-dependent attenuation stage. The device comprises a receiving section (162) adapted to receive data representing an output acoustic signal (140) from the audio reproduction system, recorded upon excitation of the audio reproduction system by a predetermined input data signal (110)a first distortion detection section (163) adapted to detect presence of non-linear distortion based on the received data and to apply psycho-acoustic compensation to the detected non-linear distortion and a control section (164) adapted to determine, based on the psycho-acoustically compensated non-linear distortion, control information (170) suitable for controlling the frequency-dependent attenuation stage.

First claim

The invention claimed is:

1. A device for tuning a frequency-dependent attenuation stage with the purpose of suppressing non-linear distortion occurring in an audio reproduction system associated with the frequency-dependent attenuation stage, the audio reproduction system being arranged to supply an output acoustic signal in response to an input data signal, the device comprising:
a receiving section adapted to receive data representing an output acoustic signal recorded upon excitation of the audio reproduction system by a predetermined input data signal;
a first distortion detection section adapted to detect presence of non-linear distortion based on the received data and to apply psycho-acoustic compensation to the detected non-linear distortion, wherein the psycho-acoustic compensation compensates for a psycho-acoustic effect influencing how the detected non-linear distortion would be perceived by a listener; and
a control section adapted to determine, based on the psycho-acoustically compensated non-linear distortion, control information suitable for controlling the frequency-dependent attenuation stage,
wherein the first distortion detection section is adapted to apply psycho-acoustic compensation by at least disregarding spectral content of the detected non-linear distortion below a frequency-dependent audibility threshold, wherein, for a given frequency, the frequency-dependent audibility threshold is set based on a threshold amplitude/power/energy level for audibility by an average human listener at the given frequency, so that at least spectral content of the detected non-linear distortion that is perceived by the average human listener as sufficiently quiet is disregarded.

2. The device of claim 1 , wherein the first distortion detection section is adapted to calibrate the frequency-dependent audibility threshold based on a sound pressure level estimated in connection with the recording of the output acoustic signal represented by the received data.

3. The device of claim 1 , wherein the first distortion detection section is adapted to apply psycho-acoustic compensation by at least:
obtaining knowledge of a first frequency component of the predetermined input data signal;
estimating, based on the first frequency component, a masking threshold for a neighborhood of the first frequency component, the masking threshold indicating frequency masking relating to a masking effect of the first frequency component on sound in the neighborhood of the first frequency component, as perceived by the average human listener; and
disregarding spectral content of the detected non-linear distortion below the masking threshold.

4. The device of claim 1 , wherein the first distortion detection section is adapted to:
obtain knowledge of a first frequency component of the predetermined input data signal; and
detect, based on the received data, non-linear distortion components corresponding to the first frequency component.

5. The device of claim 4 , wherein the first distortion detection section is adapted to determine a power ratio between the power of such spectral content of the received data that is localized substantially at the same frequency as the first frequency component and a sum of powers of said non-linear distortion components, and wherein the control section is adapted to determine the control information also based on said power ratio.

6. The device of claim 5 , wherein the first distortion detection section is adapted to apply psycho-acoustic compensation at least by normalizing, prior to forming said power ratio, the power of said spectral content of the received data and the powers of said non-linear distortion components, with respect to a frequency-dependent audibility threshold.

7. The device of any of claim 4 , wherein the first distortion detection section is adapted to apply psycho-acoustic compensation by at least:
assigning harmonic indices to said non-linear distortion components; and
applying weights to said non-linear distortion components based on said harmonic indices.

8. The device of claim 4 , wherein the first distortion detection section is adapted to apply psycho-acoustic compensation at least by estimating a loudness of said spectral content of the received data and a combined loudness of said non-linear distortion components, and wherein the control section is adapted to determine the control information also based on a difference between the estimated loudnesses.

9. The device of claim 1 , comprising a second distortion detection section adapted to:
obtain knowledge of a frequency range covering the spectral content of the predetermined input data signal; and
detect non-linear distortion based on spectral content of the received data above said frequency range,
wherein the control section is adapted to determine the control information also based on the non-linear distortion detected by the second distortion detection section.

10. The device of claim 1 , adapted to receive data recorded upon excitation of the audio reproduction system by a sequence of predetermined input data signals, consecutive predetermined input data signals in said sequence corresponding to increasingly amplified versions of a predetermined waveform, the device comprising a spectral composition analysis section adapted to:
monitor, based on the received data, the spectral composition of the output acoustic signals of the audio reproduction system resulting from excitation by said sequence of predetermined input data signals;
detect an abrupt change in the monitored spectral composition; and
determine an amplification value of said predetermined waveform corresponding to the detected abrupt change,
wherein the control section is adapted to determine the control information also based on the amplification value determined by the spectral composition analysis section.

11. The device of claim 1 , comprising a correlation analysis section adapted to determine coherence between the predetermined input data signal and the received data, wherein the control section is adapted to determine the control information also based on values of the coherence determined by the coherence analysis section.

12. The device of claim 11 , wherein the correlation analysis section is adapted to:
determine a cross-correlation between the predetermined input data signal and the received data;
estimate a sample rate difference between the predetermined input data signal and the received data based on the determined cross-correlation; and
determine said coherence based on a re-sampled version of the received data.

13. The device of claim 1 , adapted to receive data recorded upon excitation of the audio reproduction system by a sequence of predetermined input data signals, consecutive predetermined input data signals in said sequence corresponding to increasingly amplified versions of a predetermined waveform, the device comprising a dynamic range control, DRC, detection section adapted to:
monitor, based on the received data, the amplitude of the output acoustic signal from the audio reproduction system resulting from excitation of the audio reproduction system by said sequence; and
detect a saturation of the monitored amplitude, evidencing presence of DRC in the audio reproduction system,
wherein the control section is adapted to determine the control information also based on an outcome of the detection by the DRC detection section.

14. The device of claim 13 , wherein the control section is adapted to determine, in response to the detection by the DRC detection section, control information for causing the frequency-dependent attenuation

Assignees

• Dolby Int Ab
• Dolby Laboratories Licensing Corp

Inventors

• Pakarinen Jyri Tapani
• Smithers Michael
• Torres Juan Felix
• Purnhagen Heiko

Classifications

• H04S2400/09

  Electronic reduction of distortion of stereophonic sound systems · CPC title

• H04R3/04 Primary

  for correcting frequency response · CPC title

• G10L21/0232 Primary

  Processing in the frequency domain · CPC title

• H03G5/165 Primary

  Equalizers; Volume or gain control in limited frequency bands · CPC title

• H03G5/005

  of digital signals · CPC title