Method of improving the audibility of sound from a loudspeaker located close to an ear

• US 7,177,433 B2
• Filed: 03/07/2001
• Issued: 02/13/2007
• Est. Priority Date: 03/07/2000
• Status: Expired due to Term

• Current Assignee: Creative Technology Ltd.
• Original Assignee: Creative Technology Ltd.
• Inventors: Sibbald, Alastair
• Primary Examiner(s): Mei; Xu
• Application Number:
  US10/220,722
• Publication Number:
  US 20030185403A1
• Time in Patent Office: 2,169 Days
• Field of Search: 381/71.6, 381/74, 381/71.1, 381/72, 381/317, 381/318, 381/57, 381/73.1, 381/384, 381/372
• US Class Current: 381/71.6
• CPC Class Codes: G10K 11/17823 Reference signals, e.g. ambient acoustic environment
• 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 11/17857 Geometric disposition, e.g. placement of microphones
• CPC Class Codes: G10K 11/17873 using a reference signal without an error signal, e.g. pure feedforward
• 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 2210/3027 Feedforward
• CPC Class Codes: G10K 2210/3055 Transfer function of the acoustic system
• CPC Class Codes: H04M 1/19 Arrangements of transmitters, receivers, or complete sets to prevent eavesdropping, to attenuate local noise or to prevent undesired transmission; Mouthpieces or receivers specially adapted therefor circuit arrangements for preventing eavesdropping H04M1/68; telephone cabinets E04H1/14
• CPC Class Codes: H04M 1/6016 in the receiver circuit
• CPC Class Codes: H04R 3/00 Circuits for transducers , loudspeakers or microphones

Abstract

A method and apparatus for improving the audibility of sound from a loudspeaker located close to an ear, comprises the steps of detecting ambient acoustic noise arriving from other sound sources using a transducer that provides corresponding ambient sound signals, inverting the polarity of said ambient sound signals and combining them with the signals being fed to the loudspeaker to reduce the audibility of said ambient acoustic noise, and passing said ambient sound signals through a filter having a predetermined average transfer function that compensates for the spectral modification of sounds travelling from the loudspeaker to the ear caused by the proximity of the ear of a listener in use.

Claims

1. A method of improving the audibility of sound from a loudspeaker located close to an ear, comprising the steps of detecting ambient acoustic noise arriving from other sound sources using a transducer that provides corresponding ambient sound signals;

inverting the polarity of said ambient sound signals and combining them with the signals being fed to the loudspeaker to reduce the audibility of said ambient acoustic noise;

passing said ambient sound signals through a filter having a predetermined average transfer function that compensates for the spectral modification of sounds travelling from the loudspeaker to the ear caused by the proximity of the loudspeaker to the ear of a listener in use.

2. The method of claim 1 wherein the transfer function also compensates for the spectral modification of the detected ambient noise sound signal caused by the proximity of the transducer to the head of a listener in use.

3. The method of claim 1 in which the transfer function also compensates for the modification of the ambient noise sound signal caused by the proximity of the loudspeaker to the ear of a listener in use.

4. The method of claim 1 in which the transfer function is one of a plurality of transfer functions which are user-selectable in use.

5. The method of claim 1 wherein the filter is an FIR or IIR filter.

6. An apparatus for improving the audibility of sound from a loudspeaker located close to an ear, comprising:

a headphone system;

acoustic noise reduction means comprising a filter, the filter having a predetermined transfer characteristic that compensates for the spectral modification of sounds travelling from the headphone to the ear caused by the proximity of the headphone to the ear of a listener in use.

7. The apparatus of claim 6 having a ambient acoustic noise reduction means including a transducer for detecting ambient acoustic noise, and a filter having a predetermined transfer characteristic which compensates for the spectral modification of the detected ambient acoustic noise caused by the proximity of the transducer to the head of a listener in use.

8. The apparatus of claim 6 in which the filter also compensates for the modification of the ambient noise sound signal caused by the proximity of the loudspeaker to the ear of a listener in use.

9. The apparatus of claim 6 wherein said headphone system is a telephone.

10. A system for programming the transfer function of a programmable filter in a noise reduction system for improving the audibility of sound from a loudspeaker located close to an ear comprising:

a transducer located close to said loudspeaker for detecting ambient sound signals; and

signal processing means comprising;

means to invert the polarity of said ambient sound signals and combine them with the signals being fed to the loudspeaker;

a sound source for generating ambient sounds over a range of frequencies, the sound source being remote from the loudspeaker; and

control means for providing a plurality of user-selectable transfer functions which can be programmed into the programmable filter such that a user can select the optimum transfer function in use wherein the user-selectable transfer functions provide compensation for at least spectral modification of sounds travelling from the loudspeaker to the ear caused by the proximity of the loudspeaker to the ear of a listener.

11. The system as recited in claim 10 wherein the user-selectable transfer functions further provide compensation for modification of the ambient noise sound signal caused by the proximity of the loudspeaker to the ear of a listener in use.