Active Noise Reduction System Control

• US 20110002474A1
• Filed: 01/29/2010
• Published: 01/06/2011
• Est. Priority Date: 01/29/2009
• Status: Abandoned Application

• Current Assignee: Phitek Systems Limited (Amphenol Corporation)
• Original Assignee: Phitek Systems Limited (Amphenol Corporation)
• Inventors: Fuller, Graeme Colin
• Application Number:
  US12/696,197
• Publication Number:
  US 20110002474A1
• Time in Patent Office: Days
• US Class Current: 381/71.6
• CPC Class Codes: G10K 11/17817 between the output signals and the error signals, i.e. secondary path
• CPC Class Codes: G10K 11/17819 between the output signals and the reference signals, e.g. to prevent howling
• CPC Class Codes: G10K 11/17825 Error signals
• CPC Class Codes: G10K 11/1785 Methods, e.g. algorithms; Devices G10K11/1781, G10K11/1783 take precedence
• CPC Class Codes: G10K 11/17853 of the filter
• CPC Class Codes: G10K 11/17873 using a reference signal without an error signal, e.g. pure feedforward
• CPC Class Codes: G10K 11/17875 using an error signal without a reference signal, e.g. pure feedback
• CPC Class Codes: G10K 11/17881 the reference signal being an acoustic signal, e.g. recorded with a microphone
• CPC Class Codes: G10K 11/17885 additionally using a desired external signal, e.g. pass-through audio such as music or speech
• CPC Class Codes: G10K 2210/1081 Earphones, e.g. for telephones, ear protectors or headsets
• CPC Class Codes: G10K 2210/30232 Transfer functions, e.g. impulse response
• CPC Class Codes: G10K 2210/3056 Variable gain

Abstract

An active noise reduction system for use with an ear piece uses an ultrasonic signal to determine the acoustic coupling between a speaker and a sensor microphone of the noise reduction system. The determination of the acoustic coupling may be used to adjust the game of the system to provide a closed loop game which optimises performance of the system.

Claims

1. An active noise reduction system comprising:

an earpiece adapted to be held against a user'"'"'s ear,

a speaker provided within the earpiece;

a sensing microphone for sensing noise adjacent to the earpiece;

a controller for receiving a signal from the sensing microphone and providing a signal to the speaker to cancel noise in a region adjacent to the earpiece and the ear of a user;

a signal generator to generate an ultrasonic signal for provision to the speaker, and

a filter to detect a sensed signal sensed by the sensing microphone resulting from the ultrasonic signal to determine the acoustic coupling between the speaker and the sensing microphone.

2. An active noise reduction system as claimed in claim 1 wherein the system is a feedback system and the sensing microphone senses noise in the region adjacent to the earpiece and the ear of the user.

3. An active noise reduction system as claimed in claim 1 wherein the system is a feed-forward system.

4. An active noise reduction system as claimed in claim 1 wherein the acoustic coupling is used to vary a parameter of the controller to optimise the active noise reduction performance of the system.

5. An active noise reduction system as claimed in claim 4 wherein the parameter is the gain of the controller.

6. An active noise reduction system as claimed in claim 2 wherein the earpiece comprises a communications device handset, a first port acoustically connecting the speaker to the environment external to the handset, and a second port acoustically connecting the sensing microphone to the environment external to the handset.

7. An active noise reduction system as claimed in claim 1 wherein the ultrasonic frequency comprises a swept frequency.

8. An active noise reduction system as claimed in claim 1 wherein the ultrasonic frequency comprises a plurality of ultrasonic frequencies.

9. A method of optimising performance of a feedback active noise reduction system having a speaker and a sensing microphone and a controller for receiving a signal from the sensing microphone and providing a signal to the speaker to cancel noise, the method comprising:

determining a relationship between open loop acoustic coupling between the speaker and the sensing microphone and optimal closed loop gain for the system;

monitoring the open loop acoustic coupling, and;

dynamically adjusting the gain of the controller to provide a system closed loop gain according to the determined relationship.

10. A method as claimed in claim 9 wherein the open loop acoustic coupling is monitored periodically.

11. A method as claimed in claim 9 wherein the open loop gain is monitored continuously.

12. An active noise reduction handset comprising:

a speaker within the handset;

a sensing microphone within the handset;

a first port acoustically connecting the speaker to the environment external to the handset, and;

a second port acoustically connecting the sensing microphone to the environment external to the handset.