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

• US 20030185403A1
• Filed: 12/18/2002
• Published: 10/02/2003
• Est. Priority Date: 03/07/2000
• Status: Active Grant

• Current Assignee: Creative Technology Ltd.
• Original Assignee: Creative Technology Ltd.
• Inventors: Sibbald, Alastair
• Granted Patent: US 7,177,433 B2
• Time in Patent Office: Days
• 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 of improving the audibility of sound from a loudspeaker (1) located close to an ear (2) comprises detecting ambient sounds arriving from other sound sources using a transducer (3) which provides corresponding ambient sound signals, inverting the polarity of said signals, and passing the said ambient sound signals through a filter (4) having a transfer function which compensates for the spectral acoustic modification of sounds travelling from the loudspeaker to the ear caused by the proximity of the ear to the loudspeaker, and/or the proximity of the transducer to the head, and combining the filtered ambient sound signals with the signals being fed to the loudspeaker to reduce the audibility of said ambient sounds.

Claims

1. A method of improving the audibility of sound from a loudspeaker (1) located close to an ear (2), comprising detecting ambient acoustic noise arriving from other sound sources using a transducer (3) which 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, characterised in that the method includes passing the said ambient sound signals through a filter (4) having a predetermined average transfer function which 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. A method as claimed in claim 1 in which 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. A method as claimed in claim 1 or 2 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. A method as claimed in claim 1, 2 or 3 in which the transfer function is one of a plurality of transfer functions which are user-selectable in use.

5. A method as claimed in any preceding claim in which the filter is an FIR or IIR filter.

6. Apparatus for performing the method of claim 1, 2, or 3 including or consisting of a headphone system having ambient acoustic noise reduction means including a filter (4), the filter having a predetermined transfer characteristic which compensates for the spectral modification of sounds travelling from the headphone to the ear (2) caused by the proximity of the headphone to the ear of a listener in use.

7. Apparatus as claimed in claim 6 having a ambient acoustic noise reduction means including a transducer (3) for detecting ambient acoustic noise, and a filter (4) 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. Apparatus as claimed in claim 6 or 7 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. A telephone including apparatus as claimed in claim 6, 7 or 8.

10. Apparatus for performing the method of claim 1 including or consisting of a system for programming the transfer function of a programmable filter (4) in a noise reduction system for improving the audibility of sound from a loudspeaker (1) located close to an ear (2), the system including a transducer (3) located close to said loudspeaker for detecting ambient sound signals, signal processing means (5) including 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.