OBSERVER-BASED CANCELLATION SYSTEM FOR IMPLANTABLE HEARING INSTRUMENTS

• US 20090112051A1
• Filed: 10/30/2007
• Published: 04/30/2009
• Est. Priority Date: 10/30/2007
• Status: Active Grant

• Current Assignee: Otologics, LLC
• Original Assignee: Cochlear Limited
• Inventors: Miller, Scott Allan III
• Granted Patent: US 8,472,654 B2
• Time in Patent Office: Days
• US Class Current: 600/25
• CPC Class Codes: A61B 5/721 using a separate sensor to detect motion or using motion information derived from signals other than the physiological signal to be measured
• CPC Class Codes: A61N 1/36038 Cochlear stimulation
• CPC Class Codes: A61N 1/36039 fitting procedures
• CPC Class Codes: G10L 2021/065 Aids for the handicapped in understanding
• CPC Class Codes: G10L 21/0208 Noise filtering
• CPC Class Codes: H04R 2410/05 Noise reduction with a separate noise microphone
• CPC Class Codes: H04R 25/00 Deaf-aid sets , i.e. electro-acoustic or electro-mechanical hearing aids; Electric tinnitus maskers providing an auditory perception electrical stimulation of auditory nerves to promote the auditory function A61N1/36038; optical stimulation of auditory nerves to promote the auditory function A61N5/0622
• CPC Class Codes: H04R 25/43 Electronic input selection or mixing based on input signal analysis, e.g. mixing or selection between microphone and telecoil or between microphones with different directivity characteristics H04R25/407 takes precedence
• CPC Class Codes: H04R 25/453 electronically
• CPC Class Codes: H04R 25/606 acting directly on the eardrum, the ossicles or the skull, e.g. mastoid, tooth, maxillary or mandibular bone, or mechanically stimulating the cochlea, e.g. at the oval window

Abstract

Provided is an implanted hearing instrument having reduced sensitivity to vibration. In this regard, the instrument differentiates between the desirable and undesirable signals within an implanted microphone response. In one arrangement, an observer identifies a current operating state of the implanted hearing instrument and one or more cancellation filters are adjusted based on the current operating state. The cancellation filter(s) are used to reduce undesired signals form the implanted microphone response. In a first arrangement, the output of the implanted hearing instrument may be filtered and removed from the implanted microphone response to reduce or substantially eliminate feedback in the microphone signal provided to an implanted signal processor.

Claims

1. A method for use in an implantable hearing instrument having an implantable microphone, comprising:

identifying a current operating condition of an implantable hearing instrument;

establishing filter settings for a cancellation filter based on said current operating condition; and

utilizing said cancellation filter to cancel signals from a microphone output response of the implantable microphone.

2. The method of claim 1, wherein using said cancellation filter to cancel signals comprises:

filtering a digital output signal of the hearing system to generate a filtered output; and

combining the filtered output with the microphone output response to generate a net signal.

3. The method of claim 2, wherein said net signal is utilized by the hearing instrument to generate a subsequent output signal.

4. The method of claim 1, wherein identifying a current operating condition comprises:

combining a microphone output response of an implantable microphone with a motion sensor output response of a motion sensor, wherein the motion sensor output response is filtered by a filter having a transfer function associated with responses of the motion sensor and implantable microphone, and wherein combining the responses produces a first net signal;

adjusting the first filter to reduce a residual energy of said first net signal; and

upon reducing the residual energy to a desired degree, determining said operating condition based at least in part on settings of said first filter.

5. The method of claim 1, wherein said current operating condition is related to a current posture of a wearer of the implantable hearing instrument.

6. The method of claim 5, further comprising:

upon identifying the current posture of the wearer, selecting filter coefficients for said cancellation filter based on said current posture.

7. The method of claim 5, wherein selecting filter coefficients comprises interpolating said coefficients from at least two posture related models associated with said second filter.

8. The method of claim 1, wherein identifying the current operating condition comprises:

utilizing an observer to determine the operating condition, wherein the observer generates an output indicative of said operating condition.

9. The method of claim 8, wherein said filter coefficients are generated based on the output of the observer.

10. A method for use in an implantable hearing instrument having an implantable microphone, comprising:

combining a microphone output response of an implantable microphone with a motion sensor output response of a motion sensor, wherein the motion sensor output response is filtered by a first filter and wherein combining the responses produces a first net signal;

adjusting the first filter to reduce a residual energy of said first net signal; and

upon reducing the residual energy to a desired degree, utilizing settings of said first filter to establish filter settings of a second filter.

11. The method of claim 10, further comprising:

utilizing said second filter to cancel signals from a microphone output response of the implantable microphone.

12. The method of claim 11, wherein using said second filter to cancel signals comprises:

using said second filter to filter an output drive signal of the hearing system to generate a filtered output; and

combining the filtered output with the microphone output response to generate a second net signal.

13. The method of claim 12, wherein the second net signal is substantially free of electrical noise from the motion sensor.

14. The method of claim 12, further comprising:

utilizing said second net signal to generate an output drive signal for an auditory stimulator of said implantable hearing system.

15. The method of claim 12, further comprising:

utilizing a combination of said first and second net signals to generate an output drive signal for an auditory stimulator of said implantable hearing system.

16. The method of claim 10, wherein adjusting the first filter comprises:

adjusting an operating condition dependent variable that is common to multiple coefficients of said first filter.

17. The method of claim 16, wherein said operating condition dependent variable is related to a posture of a wearer of the implantable hearing instrument.

18. The method of claim 16, wherein a value of the operating condition variable that reduces the residual energy to the desired degree represents a current state of the hearing instrument and wherein utilizing filter settings of said first filter to establish filter settings of a second filter, comprises:

utilizing the value associated with the current sate of the hearing instrument to generate filter settings for the second filter.

19. The method of claim 10, wherein a first transfer function of the first filter is determined from a relationship between responses of the motion sensor and the implanted microphone and a second transfer function of the second filter is determined from a relationship between an output drive signal of the hearing instrument and a response of the implanted microphone.

20. A system for reducing noise in an output signal of an implanted hearing instrument, comprising:

an implantable microphone for receiving signals and generating a microphone output response;

a signal processor for processing received signals and generating an output signal for actuating an auditory stimulation device;

an observer for producing an output indicative of a current operating condition of the implantable hearing instrument; and

a first cancellation filter for filtering said output signal and removing a resulting filtered response from the microphone output response to produce a first cancelled signal at least a portion of which is received by the signal processor, wherein settings of said first cancellation filter are adjusted based on the output of the observer.

21. The system of claim 20, wherein said system further comprises:

a motion sensor operative to generate a motion sensor output response indicative of motion.

22. The system of claim 21, wherein said observer comprises:

a second cancellation filter for filtering said motion sensor output response and removing a resulting filtered motion response from the microphone output response to produce a second cancelled signal.

23. The system of claim 22, wherein said second cancellation filter comprises a transfer function indicative of a relationship between output signals of motion sensor output responses and responses of the implanted microphone.

24. The system of claim 20, wherein said first cancellation filter comprises a transfer function indicative of a relationship between output signals of the signal processor and responses of the implanted microphone.