AMBIENT NOISE REDUCTION ARRANGEMENTS

• US 20140003613A1
• Filed: 06/17/2013
• Published: 01/02/2014
• Est. Priority Date: 01/26/2006
• Status: Active Grant

• Current Assignee: Cirrus Logic Incorporated
• Original Assignee: Wolfson Microelectronics plc
• Inventors: Sibbald, Alastair
• Granted Patent: US 9,786,264 B2
• Time in Patent Office: Days
• US Class Current: 381/71.6
• CPC Class Codes: G10K 11/17815 between the reference signals and the error signals, i.e. primary path
• CPC Class Codes: G10K 11/17857 Geometric disposition, e.g. placement of microphones
• CPC Class Codes: G10K 11/17861 using additional means for damping sound, e.g. using sound absorbing panels
• CPC Class Codes: G10K 11/17873 using a reference signal without an error signal, e.g. pure feedforward
• CPC Class Codes: H04R 1/1083 Reduction of ambient noise active noise reduction per se G10K11/175; protective devices for the ear, e.g. providing acoustic protection A61F11/06

Abstract

A feedforward ambient noise reduction arrangement includes, within a housing, a loudspeaker device for directing sound energy into an ear of a listener. Disposed externally of the housing, and positioned to sense ambient noise on its way to the listener'"'"'s ear, are plural microphone devices capable of converting the sensed ambient noise into electrical signals for application to the loudspeaker to generate an acoustic signal opposing the ambient noise. Importantly, the overall arrangement is such that the acoustic signal is generated by said loudspeaker means in substantial time alignment with the arrival of said ambient noise at the listener'"'"'s ear.

Claims

1. A mobile telephone handset, comprising:

a housing,

a loudspeaker mounted within the housing for generating sounds in response to signal, and for directing sound through a loudspeaker aperture to an entry location of a user'"'"'s ear when the handset is held with the loudspeaker facing the ear,

a plurality of microphones positioned to sense ambient noise,

noise cancellation circuitry for receiving input signals from the microphones, and for generating a noise cancellation signal, wherein the noise cancellation circuitry is connected to apply the noise cancellation signal to the loudspeaker,

wherein an acoustic signal generated by the loudspeaker in response to the noise cancellation signal arrives at said entry location in substantial time alignment with the arrival of the ambient noise at said entry location.

2. A mobile telephone handset as claimed in claim 1, wherein the plurality of microphones are located around the loudspeaker aperture.

3. A mobile telephone handset as claimed in claim 2, wherein the plurality of microphones are located at equal distances from the loudspeaker.

4. A mobile telephone handset as claimed in claim 1, wherein the microphones are located inside respective sound inlet ports formed in the housing.

5. A mobile telephone handset as claimed in claim 4, wherein the sound inlet ports formed in the housing open in respective different directions.

6. A mobile telephone handset as claimed in claim 5, wherein the microphones respond substantially equally to ambient sounds from said respective different directions.

7. A mobile telephone handset, comprising:

a housing;

a loudspeaker, supported within said housing;

a plurality of microphones positioned to sense ambient noise externally of said housing as said ambient noise approaches the handset from respective directions, and said microphones being adapted to convert the sensed ambient noise into electrical signals;

a summer for summing the electrical signals generated by the microphones;

a feedforward noise cancellation circuit for receiving said summed electrical signals and for applying a filter function thereto, wherein the feedforward noise cancellation circuit is connected to said loudspeaker to apply the filtered summed electrical signals thereto.

8. A mobile telephone handset as claimed in claim 7, wherein the microphones are located in a distributed array around the loudspeaker.

9. A mobile telephone handset as claimed in claim 7, wherein the microphones are located inside respective sound inlet ports formed in the housing.

10. A mobile telephone handset as claimed in claim 9, wherein the sound inlet ports formed in the housing open in respective different directions.

11. An ambient noise reducing system comprising:

a housing;

a loudspeaker, supported within said housing;

a plurality of microphones positioned to sense ambient noise approaching said housing;

circuitry for converting the sensed ambient noise into electrical signals for application to said loudspeaker to generate an acoustic signal opposing said ambient noise at an entry location;

wherein the time-of-flight of the sensed ambient noise to said entry location is matched to a system response time.

12. An ambient noise reducing system as claimed in claim 11, wherein the system response time comprises:

a loudspeaker response time; and

a time of flight of sound generated by the loudspeaker.

13. An ambient noise reducing system as claimed in claim 11, wherein the plurality of microphones are located around the loudspeaker.

14. An ambient noise reducing system as claimed in claim 11, wherein the plurality of microphones are located at equal distances from the loudspeaker.

15. An ambient noise reducing system as claimed in claim 11, wherein the microphones are located inside respective sound inlet ports formed in the housing.

16. An ambient noise reducing system as claimed in claim 15, wherein the sound inlet ports formed in the housing open in respective different directions.

17. An ambient noise reducing system comprising:

a housing;

a loudspeaker, supported within said housing;

a plurality of microphones positioned to sense ambient noise approaching said housing;

circuitry for converting the sensed ambient noise into electrical signals for application to said loudspeaker to generate an acoustic signal opposing said ambient noise at an entry location;

wherein the time-of-flight of the sensed ambient noise to said entry location is matched to the system response time, such that said acoustic signal is in substantial time alignment with the arrival of said ambient noise at said entry location.

18. An ambient noise reducing system as claimed in claim 17, wherein the system response time comprises:

a loudspeaker response time; and

a time of flight of sound generated by the loudspeaker.

19. An ambient noise reducing system as claimed in claim 17, wherein the time-of-flight of the sensed ambient noise to said entry location is matched to the system response time, such that said acoustic signal is time aligned with the arrival of said ambient noise at said entry location to 40 μ

s or less.

20. An ambient noise reducing system as claimed in claim 19, wherein the time-of-flight of the sensed ambient noise to said entry location is matched to the system response time, such that said acoustic signal is time aligned with the arrival of said ambient noise at said entry location to 25 μ

s or less.