Personal hearing control system and method

• US 20080107287A1
• Filed: 11/05/2007
• Published: 05/08/2008
• Est. Priority Date: 11/06/2006
• Status: Active Grant

• Current Assignee: Terry Beard
• Original Assignee: Terry Beard
• Inventors: Beard, Terry
• Granted Patent: US 8,027,481 B2
• Time in Patent Office: Days
• US Class Current: 381/111
• CPC Class Codes: H04R 1/1016 Earpieces of the intra-aural type
• CPC Class Codes: H04R 2460/05 Electronic compensation of the occlusion effect
• CPC Class Codes: H04R 2460/15 Determination of the acoustic seal of ear moulds or ear tips of hearing devices
• CPC Class Codes: H04S 2420/01 Enhancing the perception of the sound image or of the spatial distribution using head related transfer functions [HRTF's] or equivalents thereof, e.g. interaural time difference [ITD] or interaural level difference [ILD]
• CPC Class Codes: H04S 7/30 Control circuits for electronic adaptation of the sound field

Abstract

A personal hearing control system includes a microphone located within a user'"'"'s sealed ear canal, a speaker having a diaphragm which directs sound into the ear canal, and a controller which drives the speaker such that the system emulates the acoustics of the user'"'"'s open ear canal. Also provided are a microphone located on the outer ear side of the sealed ear canal, which is coupled to a handheld interface unit having multiple inputs and operating modes. A user-selected input is processed by the interface unit, and the processed signal is coupled to the speaker. In one operating mode, the output of the outer ear mic is processed so as to cancel sound that leaks from the outer ear to the inner ear side of the seal.

Claims

1. A personal hearing control system, comprising:

an ear canal microphone suitable for placement within a user'"'"'s ear canal;

a speaker suitable for placement between said ear canal microphone and said user'"'"'s outer ear, said speaker including a diaphragm which directs sound into said user'"'"'s ear canal in response to a driving signal, said ear canal microphone arranged to produce an output signal which varies with the instantaneous pressure in said ear canal; and

a controller which receives the output signal from said ear canal microphone and provides said driving signal to said speaker, said controller arranged to control the relationship between the instantaneous pressure in said ear canal and said diaphragm'"'"'s velocity such that said velocity is proportional to said instantaneous pressure over the range of sound frequencies that would normally be affected by the occlusion effect.

2. The system of claim 1, wherein said controller is arranged such that said system emulates the acoustics of said user'"'"'s open ear canal.

3. The system of claim 1, wherein said controller comprises an amplifier circuit arranged to operate as an inverting integrator, said amplifier circuit comprising:

an operational amplifier; and

a capacitor connected between the output of said operational amplifier and its inverting input,

said inverting input coupled to a signal which varies with the output signal from said ear canal microphone, said amplifier circuit arranged such that said driving signal used to drive said speaker'"'"'s diaphragm varies with said operational amplifier output.

4. The system of claim 3, wherein said amplifier circuit further comprises a resistor connected in series between said signal that varies with the output signal from said ear canal microphone and said inverting input, said ear canal microphone, said controller and said speaker forming a closed loop feedback system arranged such that the current flowing through said resistor into the node at said inverting input is equal to the current flowing from said node through said capacitor to said operational amplifier output, such that the effective acoustic impedance of said diaphragm varies with the resistance of said resistor.

5. The system of claim 4, wherein said speaker has an associated mechanical resonance frequency, said speaker arranged such that said mechanical resonance frequency is greater than a critical frequency CF given by:

6. The system of claim 3, further comprising a resistor connected in parallel with said capacitor, said system having an associated minimum audio frequency of interest (F_min), the resistance R of said resistor and the capacitance C of said capacitor selected such that F_min≧

RC.

7. The system of claim 1, further comprising:

a sealing means which substantially seals a user'"'"'s ear canal when worn; and

a vent through said sealing means which equalizes the air pressure between the inner ear and outer ear sides of said sealing means, said ear canal microphone and said speaker positioned on the inner ear side of said seal.

8. The system of claim 7, wherein said system has an associated minimum audio frequency of interest (F_min) and said vent is arranged to substantially attenuate audio frequencies above F_min.

9. The system of claim 1, further comprising an interface unit having one or more inputs suitable for connection to respective sources of audio, said interface unit arranged to produce an output that varies with the audio received at a user-selected input and to couple said output to said speaker.

10. The system of claim 9, wherein said interface unit is arranged such that said output is coupled to said speaker wirelessly.

11. The system of claim 9, further comprising an outer ear microphone suitable for placement on the outer ear side of said speaker, the output of said outer ear microphone coupled to an input of said interface unit, said interface unit arranged to process the output of said outer ear microphone and couple said processed output to said speaker.

12. The system of claim 11, wherein said interface unit has multiple selectable operating modes, said interface unit arranged such that the characteristics of said processed output vary with said operating modes.

13. The system of claim 12, wherein said system is arranged to substantially seal a user'"'"'s ear canal when worn such that said ear canal microphone and said speaker are on the inner ear side of said seal and said outer ear microphone is on the outer ear side of said seal, said interface unit arranged such that in a first operating mode, said interface unit is arranged to process the output of said outer ear microphone such that a signal is coupled to said speaker which cancels sound that leaks from the outer ear side of said seal to the inner ear side of said seal, and in a second operating mode, said interface unit is arranged to process the output of said outer ear microphone such that sound picked up by said outer ear microphone is coupled to said speaker such that it is reproduced for said user.

14. The system of claim 13, wherein said interface unit includes at least one finite impulse response (FIR) filter arranged to effect said sound leakage cancellation.

15. The system of claim 11, wherein said system includes a mold arranged to fill the entire concha of said user'"'"'s ear such that said user'"'"'s ear canal is substantially sealed, said system arranged such that said outer ear microphone is mounted flush on the outer surface of said mold such that the effect of said user'"'"'s pinna and ear canal response transfer function on the audio performance of said system is negligible.

16. The system of claim 15, wherein said system is arranged such that the occlusion effect that would otherwise be experienced by said user is substantially reduced and a signal is coupled to said speaker which cancels sound that leaks from the outer ear side of said seal to the inner ear side of said seal, thereby enabling 3D audio cues present in the audio signal produced by said outer ear microphone to be adopted by said user as an internally consistent set of 3D audio cues and said system to act as a standard platform for 3D audio.

17. The system of claim 11, wherein said interface unit includes a frequency equalizer adjusted such that sound picked up by said outer ear microphone is coupled to said speaker such that it is reproduced for said user with desired frequency characteristics.

18. The system of claim 1, wherein said system comprises first and second ear canal microphones, speakers, and controllers, for use by said user in respective ears.

19. A personal hearing control system, comprising:

a sealing means which substantially seals a user'"'"'s ear canal when worn, said sealing means including a vent which equalizes the air pressure between the inner ear and outer ear sides of said sealing means;

a ear canal microphone suitable for placement within a user'"'"'s ear canal on the inner ear side of said sealing means;

a speaker suitable for placement within said user'"'"'s ear canal on the inner ear side of said sealing means, said speaker including a diaphragm which directs sound into said user'"'"'s ear canal in response to a driving signal, said ear canal microphone arranged to produce an output signal which varies with the instantaneous pressure in said ear canal;

a controller which receives the output signal from said ear canal microphone and provides said driving signal to said speaker, said controller arranged to control the relationship between the instantaneous pressure in said ear canal and said diaphragm'"'"'s velocity such that said velocity is proportional to said instantaneous pressure over the range of sound frequencies that would normally be affected by the occlusion effect in said sealed ear canal, such that the occlusion effect is substantially reduced;

an interface unit having one or more inputs suitable for connection to respective sources of audio, said interface unit arranged to produce an output that varies with the audio received at a user-selected input and to couple said output to said speaker; and

an outer ear microphone suitable for placement on the outer ear side of said sealing means, the output of said outer ear microphone coupled to an input of said interface unit, said interface unit arranged to process the output of said outer ear microphone and couple said processed output to said speaker,

wherein said interface unit has multiple selectable operating modes, said interface unit arranged such that in a first operating mode, the output of said outer ear microphone is processed such that the output coupled to said speaker cancels sound that leaks from the outer ear side of said seal to the inner ear side of said seal, and in a second operating mode, the output of said outer ear microphone is processed such that sound picked up by said outer ear microphone is coupled to said speaker such that it is reproduced for said user.

20. A method of controlling the sound perceived by a user, comprising:

providing a means of substantially sealing a user'"'"'s ear canal;

providing a speaker on the inner ear side of said sealing means having a diaphragm suitable for directing sound into said user'"'"'s ear canal in response to a driving signal;

measuring the instantaneous pressure in said ear canal;

controlling the relationship between the instantaneous pressure in said ear canal and said diaphragm'"'"'s velocity such that said velocity is proportional to said instantaneous pressure over the range of sound frequencies that would normally be affected by the occlusion effect, such that the occlusion effect is substantially reduced, thereby enabling the acoustics of said user'"'"'s open ear canal to be emulated;

providing an outer ear microphone suitable for placement on the outer ear side of said sealing means;

providing a means for receiving audio signals from one or more sources including said outer ear microphone; and

providing said driving signal such that it varies with one of said received audio signals.

21. The method of claim 20, wherein said instantaneous pressure is measured using an ear canal microphone suitable for placement within a user'"'"'s ear canal, further comprising:

determining the system transfer function between the audio signal produced by said outer ear microphone and the output of said ear canal microphone;

determining the system transfer function between said speaker and the output of said ear canal microphone;

implementing at least one filter based on said system transfer functions; and

using said at least one filter to process the audio signal produced by said outer ear microphone such that a signal is coupled to said speaker which cancels sound that leaks from the outer ear side of said seal to the inner ear side of said seal.

22. The method of claim 21, wherein said at least one filter is at least one finite impulse response (FIR) filter, further comprising calculating the coefficients of said at least one finite impulse response (FIR) filter based on said system transfer functions.

23. The method of claim 22, further comprising providing a means of automatically determining said system transfer functions and recalculating said coefficients.

24. The method of claim 21, further comprising:

implementing at least one additional filter based on said system transfer functions; and

using said at least one additional filter to process the audio signal produced by said outer ear microphone such that sound picked up by said outer ear microphone is coupled to said speaker such that it is reproduced for the user with desired frequency characteristics.

25. The method of claim 20, further comprising processing the audio signal produced by said outer ear microphone such that sound picked up by said outer ear microphone is reproduced for said user, and a signal is coupled to said speaker which cancels sound that leaks from the outer ear side of said seal to the inner ear side of said seal, thereby enabling 3D audio cues present in the audio signal produced by said outer ear microphone to be adopted by a user as an internally consistent set of 3D audio cues.