Accoustically transparent occlusion reduction system and method
A system and method that reduces the perceptual effect resulting from ear occlusion include an electro-acoustic feedback network that produces phase canceling sounds in the ear, where a receiver and a microphone are located. A control mechanism controls the response of the feedback network to minimize distortion in the ear while maintaining a desired frequency response for external signals. Devices producing the external signal include hearing aids, personal sound devices, in ear monitors, communications headsets and hearing protectors. The integration of the above with these devices improves a user's perception of their own voice.
1. An electro-acoustic system including:
an electro-acoustic circuit including a negative-feedback loop, the negative feedback loop comprising of:
a microphone for generating an internal signal from an acoustical signal located within or closely coupled to an occluded or partially occluded ear;
a second electronic circuit (B) for modifying the internal signal to produce a processed internal signal;
a combiner for combining the processed internal signal with a processed external signal to produce a combined signal;
a first electronic circuit (A) for modifying the combined signal to produce a receiver signal; and
a receiver for generating an acoustical signal from the receiver signal at a location within or closely coupled to the occluded or partially occluded ear;
the electro-acoustic circuit further comprising of:
a third electronic circuit (C) for modifying an external signal to produce the processed external signal; and
a fourth electronic circuit (D) for estimating the level of the receiver signal either directly from the receiver signal or from the combined signal and producing a control signal from this estimate;
wherein the processing performed by the second electronic circuit (B) is controlled by the control signal.
2. A system as claimed in claim 1 wherein the negative-feedback loop includes filtering that alters the open loop response so that the real component of the response is large and negative at frequencies where the occlusion effect is most apparent.
3. A system as claimed in claim 1 wherein the third electronic circuit (C) includes filtering that provides compensation for the closed response of the negative-feedback loop.
4. A system as claimed in claim 3 wherein the filtering provided by the third electronic circuit (C) is adaptive and controlled by the control signal.
5. A system as claimed in claim 4 wherein the fourth electronic circuit (D) estimates the level of the internal signal or the level of the processed internal signal and uses this estimate with the estimate of the receiver signal to produce a control signal.
6. A system as claimed in claim 4 or claim 5 wherein the ear is occluded or partially occluded by an earmold.
7. A system as claimed in claim 6 wherein the earmold contains a vent.
8. A system as claimed in claim 7 wherein the vent contains an acoustic damper.
9. A system as claimed in claim 4 or claim 5 wherein at least one of the electronic circuits is digital and uses a sampling rate at least four times the bandwidth of the signal.
10. An electro-acoustic system including:
an electro-acoustic circuit including a negative-feedback loop, the negative feedback loop comprising of:
a microphone for generating an internal signal from an acoustical signal located within or closely coupled to an occluded or partially occluded ear;
a second electronic circuit (B) for modifying the internal signal to produce a processed internal signal;
a combiner for combining the processed internal signal with a processed external signal to produce a combined signal;
a first electronic circuit (A) for modifying the combined signal to produce a receiver signal; and
a receiver for generating an acoustical signal from the receiver signal at a location within or closely coupled to the occluded or partially occluded ear;
the electro-acoustic circuit further comprising of:
a third electronic circuit (C) for modifying an external signal to produce the processed external signal; and
a fourth electronic circuit (D) for estimating the level of the receiver signal and producing a control signal from this estimate;
wherein the control signal controls the processing performed by the second electronic circuit (B) and controls the processing performed by the third electronic circuit (C).
11. A method of providing a negative feedback loop for an electro-acoustic system, the method including the steps of:
(a) generating an internal signal representing an acoustical signal located within or closely coupled to an occluded or partially occluded ear;
(b) modifying the internal signal to produce a processed internal signal;
(c) combining the processed internal signal with a processed external signal to produce a combined signal;
(d) modifying the combined signal to produce a receiver signal;
(e) generating an acoustical signal from the receiver signal at a location within or closely coupled to the occluded or partially occluded ear;
(f) modifying an external signal to produce the processed external signal; and
(g) estimating the level of the receiver signal either directly from the receiver signal or from the combined signal and producing a control signal from this estimate;
wherein of modification in step (b) is controlled by the control signal.
12. A method as claimed in claim 11 wherein the control signal is utilised to control the modification occurring in step (f).
13. An electro-acoustic system including:
an electro-acoustic circuit including a negative-feedback loop, the negative feedback loop comprising of:
a microphone for generating an internal signal from an acoustical signal located within or closely coupled to an occluded or partially occluded ear;
a second electronic circuit (B) for modifying the internal signal to produce a processed internal signal;
a combiner for combining the processed internal signal with a processed external signal to produce a combined signal;
a first electronic circuit (A) for modifying the combined signal to produce a receiver signal; and
a receiver for generating an acoustical signal from the receiver signal at a location within or closely coupled to the occluded or partially occluded ear;
the electro-acoustic circuit further comprising of:
a third electronic circuit (C) for modifying an external signal to produce the processed external signal; and
a fourth electronic circuit (D) for estimating the level of the receiver signal and producing a control signal from this estimate;
wherein the control signal controls the processing performed by first electronic circuit (A) and controls the processing performed by the third electronic circuit (C).
14. A system as claimed in claim 13 wherein the negative-feedback loop includes filtering that alters the open loop response so that the real component of the response is large and negative at frequencies where the occlusion effect is most apparent.
15. A system as claimed in claim 13 wherein the third electronic circuit (C) includes filtering that provides compensation for the closed response of the negative-feedback loop.
16. A system as claimed in claim 15 wherein the filtering provided by the third electronic circuit (C) is adaptive and controlled by the control signal.
17. A system as claimed in claim 16 wherein the fourth electronic circuit (D) estimates the level of the internal signal or the level of the processed internal signal and uses this estimate with the estimate of the receiver signal to produce a control signal.
18. A system as claimed in claim 16 or claim 17 wherein the ear is occluded or partially occluded by an earmold.
19. A system as claimed in claim 18 wherein the earmold contains a vent.
20. A system as claimed in claim 19 wherein the vent contains an acoustic damper.
21. A system as claimed in claim 16 or claim 17 wherein at least one of the electronic circuits is digital and uses a sampling rate at least four times that of the bandwidth of the signal.