Active noise cancelling device and method of actively cancelling acoustic noise

Patent metadata

Field	Value
Publication number	US-10325584-B2
Application number	US-201514863228-A
Country	US
Kind code	B2
Filing date	Sep 23, 2015
Priority date	Dec 10, 2014
Publication date	Jun 18, 2019
Grant date	Jun 18, 2019

Abstract

An active noise cancelling device including a sensor configured to convert acoustic signals into first audio signals and a speaker acoustically coupled to the sensor A control stage is configured to control the speaker based on the first audio signals to cause the speaker to produce cancelling acoustic waves that tend to suppress acoustic noise components in the acoustic signals. The control stage includes sigma-delta modulator digital filters.

First claim

The invention claimed is:

1. An active noise cancelling device, comprising:
a sensor configured to detect acoustic signals and to convert the detected acoustic signals into first audio signals;
a speaker acoustically coupled to the sensor; and
a control stage configured to control the speaker based on the first audio signals to produce cancelling acoustic waves that tend to suppress acoustic noise components in the acoustic signals, the control stage including sigma-delta modulator digital filters configured to suppress signal components of the first audio signals corresponding to the acoustic noise components in the acoustic signals detected by the sensor, the control stage further including a processing module including a gain stage configured to apply a gain to an input signal received from the sigma-delta modulator digital filters and to provide an output based on the input signal to a plurality of low pass filter circuits coupled in series, wherein each sigma-delta modulator digital filter has a cascade-of-integrators structure coupled in series with a quantizer to generate a quantized acoustic noise signal in logarithmic multibit format, the cascade-of-integrators structure of each sigma-delta modulator digital filter including:
a plurality of adder modules including a first adder module and a final adder module coupled to the quantizer;
a plurality of integrator modules alternately coupled in series with the plurality of adder modules between the first and final adder modules; and
an internal feedback filter module coupled to provide a feedback signal from an output of one of the plurality of integrator modules to an input of one of the plurality of adder modules.

2. The device according to claim 1 , wherein the sigma-delta modulator digital filters have a transfer function configured to cancel acoustic noise at the sensor.

3. The device according to claim 2 , wherein the sigma-delta modulator digital filters include a peak filter, a notch filter and a shelf filter.

4. The device according to claim 1 , wherein the quantizer comprises a logarithmic quantizers.

5. The device according to claim 1 , wherein at least one of the sigma-delta modulator digital filters has a zero at the Nyquist frequency.

6. The device according to claim 1 , wherein the first audio signals are in multibit PDM format.

7. The device according to claim 1 , wherein the control stage comprises a processing module configured to convert a second audio signal received from the sigma-delta modulator digital filters into a third audio signal in PCM format.

8. The device according to claim 7 , wherein the processing module has a low-pass transfer function and a bandpass gain greater than unity.

9. The device according to claim 8 , comprising a signal processing stage configured to receive an input signal and to convert the input signal into a fourth audio signal in PCM format.

10. The device according to claim 9 , wherein the signal processing stage comprises further sigma-delta modulator digital filters.

11. The device according to claim 10 , comprising a driving stage configured to drive the speaker based on a combination of the third audio signal and fourth audio signal.

12. An electronic device, comprising:
at least one playback unit, each playback unit including,
a casing;
an acoustic sensor that in operation converts detected acoustic signals into first audio signals;
a speaker acoustically coupled to the acoustic sensor; and
control stage circuitry being housed within the casing and electrically coupled to the acoustic sensor and the speaker, the control stage circuitry including a sigma-delta modulator that in operation filters the first audio signals to suppress signal components of the first audio signals corresponding to the acoustic noise components in the detected acoustic signals, and the control stage circuitry in operation controlling the speaker based on the filtered first audio signals to generate cancelling acoustic waves that reduce acoustic noise components in the detected acoustic signals, the control stage circuitry including a sigma-delta modulator digital filter having a cascade-of-integrators filter including a plurality of adders and a plurality of integrators coupled alternately in series between a first one of the plurality of adders and a final one of the plurality of adders, and including a logarithmic quantization circuit coupled to the final one of the plurality of adders, and the control stage further configured to receive a filtered signal from the sigma-delta modulator digital filter and to apply a gain to and to low pass filter the filtered signal to generate an acoustic noise signal that is added to an input audio signal provided to the speaker.

13. The electronic device according to claim 12 , wherein each playback unit is an earpiece.

14. The electronic device of claim 12 , wherein the at least one playback unit comprises two playback units that form left and right earpieces contained in a headphone assembly.

15. A method for active noise cancelling, comprising:
detecting acoustic signals present in a spatial region, the acoustic signals including acoustic noise components;
converting the detected acoustic signals present in the spatial region into first electrical audio signals having a multibit pulse density modulation coding with a single bit for a sample value and a plurality of bits for sample weight;
sigma-delta modulator filtering through a cascade-of-integrators feedback structure the first electrical audio signals to attenuate signal components of the first electrical audio signals that correspond to the acoustic noise components of the detected acoustic signal;
logarithmically quantizing the filtered first electrical audio signals to generate a quantized acoustic noise signal having a multibit pulse density format;
applying a gain to the quantized acoustic noise signal to provide an amplified quantized acoustic noise signal;
low pass filtering the amplified quantized acoustic noise signal to generate a low pass filtered amplified quantized acoustic noise signal;
generating acoustic noise cancelling signals based on the low pass filtered amplified quantized acoustic noise signal; and
producing cancelling acoustic waves in the first spatial region based on the generated acoustic noise cancelling signals, the produced cancelling acoustic waves attenuating the acoustic noise components of the detected acoustic signals.

16. The method of claim 15 , wherein sigma-delta modulator filtering the first electrical audio signals and generating acoustic noise cancelling signals comprise peak filtering followed by notch filtering followed by shelf filtering of the detected acoustic signals.

17. The method of claim 16 , wherein producing cancelling acoustic waves comprises controlling a speaker based on the generated acoustic noise cancelling signals.

18. The method of claim 15 , wherein converting the detected acoustic signals present in the spatial region into first electrical audio signals comprises converting acoustic signals present in an ear of a person into the first electrical audio signals.

Assignees

• St Microelectronics Srl
• Stmicroelectronics Shenzhen R&D Co Ltd

Inventors

• Molinari Luca
• Ma Xi Chun
• Feste Sandro Dalle
• Zerbini Martino

Classifications

• G10K11/178 Primary

  by electro-acoustically regenerating the original acoustic waves in anti-phase · CPC title

• G10K2210/3051

  Sampling, e.g. variable rate, synchronous, decimated or interpolated · CPC title

• G10K2210/3028

  Filtering, e.g. Kalman filters or special analogue or digital filters · CPC title

• H04R1/1083 Primary

  Reduction of ambient noise (active noise reduction per se G10K11/175; protective devices for the ear, e.g. providing acoustic protection A61F11/06) · CPC title

• H04R2460/01

  Hearing devices using active noise cancellation · CPC title