Audio processor with linear and non-linear modeling including limiter

Patent metadata

Field	Value
Publication number	US-10104473-B2
Application number	US-201715498800-A
Country	US
Kind code	B2
Filing date	Apr 27, 2017
Priority date	Apr 29, 2016
Publication date	Oct 16, 2018
Grant date	Oct 16, 2018

Abstract

Embodiments of the invention provide methods and apparatus for processing audio input signals, for example, so as to linearize the output of a given loudspeaker. An audio processor is provided, for modifying an audio signal to be provided to a loudspeaker, the audio processor comprising: a first filter stage, for applying to an audio signal a linear model describing an excursion of the loudspeaker in response to a given input signal, the linear model containing only linear terms, and for generating one or more excursion signals; a plurality of second filters for receiving the one or more excursion signals, each of the second filters configured to apply to a respective one of a plurality of frequency bands in the one or more excursion signals the inverse of a model describing an excursion of the loudspeaker in response to a given input signal; and a combiner for combining the outputs of each of the plurality of second filters. At least a first one of the plurality of second filters applies the inverse of a non-linear model describing an excursion of the loudspeaker in response to a given input signal, the non-linear model comprising one or more non-linear parameters.

First claim

The invention claimed is:

1. An audio processor, for modifying an audio signal to be provided to a loudspeaker, the audio processor comprising:
a first filter stage, for applying to an audio signal a linear model describing an excursion of the loudspeaker in response to a given input signal, the linear model containing only linear terms, and for generating one or more excursion signals;
a plurality of second filters for receiving the one or more excursion signals, each of the second filters configured to apply to a respective one of a plurality of frequency bands in the one or more excursion signals the inverse of a model describing an excursion of the loudspeaker in response to a given input signal;
a combiner for combining outputs of each of the plurality of second filters; and
a limiter block configured to modify the one or more excursion signals so as to prevent the loudspeaker from exceeding an excursion limit,
wherein at least a first one of the plurality of second filters applies the inverse of a non-linear model describing an excursion of the loudspeaker in response to a given input signal, the non-linear model comprising one or more non-linear parameters.

2. The audio processor as set out in claim 1 , wherein the non-linear model further comprises one or more linear parameters.

3. The audio processor as set out in claim 2 , wherein the non-linear model comprises the linear model and the one or more non-linear parameters.

4. The audio processor as set out in claim 1 , wherein at least a second one of the plurality of second filters applies to its respective frequency band the inverse of the linear model.

5. The audio processor as set out in claim 1 , wherein the limiter block is arranged between the first filter stage and the plurality of second filters.

6. The audio processor as set out in claim 1 , further comprising:
an input for receiving an input audio signal; and
a splitter configured to split the input audio signal into at least a high-frequency signal and a low-frequency signal,
wherein the low-frequency signal is provided to the first filter stage as the audio signal.

7. The audio processor as set out in claim 6 , wherein the combiner is further arranged to combine the outputs of the plurality of second filters with the high-frequency signal.

8. The audio processor as set out in claim 1 , further comprising:
a module configured to receive a respective frequency band of an excursion signal of the one or more excursion signals, determine the one or more non-linear parameters based on the excursion signal, and provide the one or more non-linear parameters to at least the first one of the plurality of second filters.

9. The audio processor as set out in claim 1 , wherein the linear model describes the excursion of the loudspeaker in response to a given input signal and a given amplification response.

10. The audio processor as set out in claim 1 , wherein the non-linear model describes the excursion of the loudspeaker in response to a given input signal and a given amplification response.

11. The audio processor as set out in claim 1 , wherein the one or more non-linear parameters comprise the force-factor of the loudspeaker.

12. The audio processor as set out in claim 1 , wherein the one or more non-linear parameters comprise an effective stiffness of a suspension of the loudspeaker.

13. The audio processor as set out in claim 1 , wherein the one or more non-linear parameters comprise Thiele-Small parameters.

14. The audio processor as set out in claim 1 , wherein the linear terms comprise Thiele-Small parameters.

15. An electronic device comprising:
an audio processor for modifying an audio signal to be provided to a loudspeaker, the audio processor comprising:
a first filter stage, for applying to an audio signal a linear model describing an excursion of the loudspeaker in response to a given input signal, the linear model containing only linear terms, and for generating one or more excursion signals;
a plurality of second filters for receiving the one or more excursion signals, each of the second filters configured to apply to a respective one of a plurality of frequency bands in the one or more excursion signals the inverse of a model describing an excursion of the loudspeaker in response to a given input signal;
a combiner for combining outputs of each of the plurality of second filters; and
a limiter block configured to modify the one or more excursion signals so as to prevent the loudspeaker from exceeding an excursion limit,
wherein at least a first one of the plurality of second filters applies the inverse of a non-linear model describing an excursion of the loudspeaker in response to a given input signal, the non-linear model comprising one or more non-linear parameters.

16. The electronic device as set out in claim 15 , wherein the electronic device is at least one of: a portable device; a battery powered device; a communications device; a computing device; a mobile telephone; a laptop, notebook or tablet computer; a personal media player; a gaming device; and a wearable device.

Assignees

• Cirrus Logic Int Semiconductor Ltd
• Cirrus Logic Inc

Inventors

• Bjork Ylva Ellen Maria
• LINDAHL Erik Vilhelm

Classifications

• H04R2430/03

  Synergistic effects of band splitting and sub-band processing · CPC title

• H04R3/08 Primary

  of electromagnetic transducers · CPC title

• H04R2499/11

  Transducers incorporated or for use in hand-held devices, e.g. mobile phones, PDA's, camera's · CPC title

• H04R29/001

  for loudspeakers (H04R29/007 takes precedence) · CPC title

• G10L21/038

  using band spreading techniques · CPC title