Method and Device to Maintain Audio Content Level Reproduction

• US 20090220096A1
• Filed: 11/26/2008
• Published: 09/03/2009
• Est. Priority Date: 11/27/2007
• Status: Active Grant

• Current Assignee: Staton Techiya, LLC
• Original Assignee: Personics Holdings, Inc.
• Inventors: Usher, John, Goldstein, Steven
• Granted Patent: US 8,855,343 B2
• Time in Patent Office: Days
• US Class Current: 381/57
• CPC Class Codes: H03G 3/32 the control being dependent upon ambient noise level or sound level
• CPC Class Codes: H03G 9/005 of digital or coded signals
• CPC Class Codes: H03G 9/18 for tone control and volume expansion or compression

Abstract

An earpiece and method to control a level of audio reproduction within an occluded ear canal can include the steps of measuring an ambient sound level from an Ambient Sound Microphone (ASM) at an entrance to an occluded ear canal, measuring a residual background noise level within an occluded ear canal from an Ear Canal Microphone (ECM), measuring a level of audio content delivered to the occluded ear canal, and adjusting a gain of the audio content so as to maintain reproduction of audio content within a predetermined level range.

Claims

1. A method to control a level of audio reproduction within an occluded ear canal, the method comprising the steps of:

measuring an ambient sound level from an Ambient Sound Microphone (ASM) at an entrance to an occluded ear canal;

measuring a residual background noise level within the occluded ear canal from an Ear Canal Microphone (ECM);

measuring a level of audio content delivered to the occluded ear canal; and

adjusting a gain of the audio content so as to maintain reproduction of audio content within a predetermined level range.

2. The method of claim 1, wherein the step of measuring a level of audio content includes:

measuring a digital level of the audio content prior to audible reproduction out of an Ear Canal Receiver (ECR); and

compensating the level by applying an Ear Canal Transfer function (ECTF) of the occluded ear canal to the audio content to estimate the audible level within the ear canal.

3. The method of claim 1, wherein the step of measuring a level of audio content includes:

measuring an analog level of the audio content reproduced in the occluded ear canal during periods of silence to determine the direct sound exposure;

measuring an analog level of residual background noise in the occluded ear canal during periods of audio content silence to determine a secondary sound exposure; and

updating the level of audio content based on the sum of the analog level of the audio content and the analog level of residual background noise.

4. The method of claim 1, where the step of adjusting a gain of the audio content further comprises:

assessing a sound exposure level to ensure the gain does not exceed a safe listening level.

5. The method of claim 1, where the step of adjusting a gain of the audio content further comprises:

increasing the gain of the audio content if a residual background noise within the occluded ear canal increases so as to achieve a constant ratio of the level of audio content to residual background noise level;

or

decreasing the gain of the audio content if a residual background noise within the occluded ear canal decreases so as to achieve the constant ratio.

6. The method of claim 1, further comprising:

adjusting a pass-through gain of ambient sound from the ASM to an Ear Canal Receiver (ECR) to decrease a reproduction gain of the ambient sound in the occluded ear canal.

7. The method of claim 6, further comprising:

assessing a sound exposure level within the occluded ear canal; and

decreasing the pass-through gain if the sound exposure level approaches or exceeds a safe listening level.

8. The method of claim 6, further comprising:

increasing the gain of the audio content if a residual background noise within the occluded ear canal increases so as to achieve a constant ratio of the level of audio content to residual background noise level, while

decreasing the pass-through gain if the sound exposure level approaches or exceeds a safe listening level.

9. The method of claim 6, further comprising:

measuring a first level of an Audio Content signal using a slow time weighting function to give a signal AC_RMS; and

measuring a second level of an Audio Content signal using a fast time weighting function to give a signal Frame-RMS.

10. The method of claim 9, further comprising:

measuring the Ear Canal Background Noise Level to give a third level EC_BNL; and

measuring a forth signal level of a processed Audio Content signal using a fast time weighting function to give a level AC_ECR

11. The method of claim 1, further comprising dynamically compressing a delayed input audio content signal to produce a modified audio content signal, where the compressing maps a first input signal level to a second output signal level at three points:

an input signal level AC_LAL, which is a Lowest Audible Level of the input Audio Content signal, taken to approximate the threshold of hearing;

an input level equal to a long-term RMS of the audio content signal, AC_RMS, and

an input level equal to a maximum possible input level AC_PK of the audio content signal reproduced with the ECR.

12. The method of claim 11, where the threshold of hearing is approximately 30 dB SPL.

13. The method of claim 11, where the maximum possible input level AC_PK does not clip, cause distortion above a predetermined level, or exceed an uncomfortable listening level.

14. The method of claim 11, where compressing is dynamically performed across sub-bands of the audio content signal.

15. The method of claim 11, where the audio content is received from a mobile device, laptop, cell phone, media player, or computer.

16. A method to control a level of audio reproduction within an occluded ear canal, the method comprising the steps of:

delivering audio content to the occluded ear canal;

measuring an ambient sound level from an Ambient Sound Microphone (ASM) at an entrance to an occluded ear canal;

measuring a residual background noise level within the occluded ear canal from an Ear Canal Microphone (ECM);

determining a sound exposure level of the audio content delivered to the occluded ear canal; and

adjusting a gain of the audio content based on the residual background noise level and sound exposure level so as to maintain reproduction of audio content within a preferred listening level and within a safe listening level.

17. The method of claim 16, comprising:

identifying periods of silence in the audio content;

estimating residual background noise level within the ear canal during the silence; and

compensating the sound exposure level for the residual background noise level.

18. The method of claim 16, comprising:

subtracting a frequency-dependant or signal-valued attenuation of an ear sealing from the ambient sound level to estimate a residual background noise level within the occluded ear canal.

19. The method of claim 16, comprising:

subtracting an equivalent Sound Pressure Level (SPL) of the Audio Content signal from the sound exposure level of the audio content to SPL_ECM to estimate a residual background noise level within the occluded ear canal.

20. An earpiece comprising:

an Ambient Sound Microphone (ASM) configured to measure ambient sound at an entrance to an occluded ear canal and produce an electronic ambient signal;

an Ear Canal Receiver (ECR) to deliver reproduced audio content to the occluded ear canal;

an Ear Canal Microphone (ECM) configured to measure sound in the occluded ear canal and produce an electronic internal signal; and

a processor operatively coupled to the ASM, the ECM and the ECR where the processor is configured to

determine a residual background noise level within the occluded ear canal by way of the Ear Canal Microphone (ECM);

determine a sound exposure level of the audio content delivered to the occluded ear canal; and

adjust a gain of the audio content in view of the residual background noise level and sound exposure level so as to maintain reproduction of the audio content in the occluded ear canal within a preferred listening level and within a safe listening level.

21. The earpiece of claim 20, where the processor applies dynamic compression to the audio content at three points along a compression curve:

a first input signal level AC_LAL point, which is a Lowest Audible Level of the input Audio Content signal, taken to approximate the threshold of hearing;

a second input level point equal to a long-term RMS of the audio content signal, AC_RMS, and

a third input level point equal to a maximum possible input level AC_PK of the audio content signal reproduced with the ECR.

22. The earpiece of claim 21, where a value of an output level signal (LCL) is approximately half a value of the residual ear canal background noise level (EC_BNL), and a value of LCL is approximately half the value of an audio content lowest audible level (AC_LAL).

23. The earpiece of claim 21, where a value of MCL is increased when the level difference between AC_ECR and an Ear Canal BNL (EC_BNL) is less than a predetermined threshold value C_SNR, where C_SNR is a level manually set by a user of the earpiece.

24. The earpiece of claim 21, where a value of MCL is decreased when a level difference between AC_ECR and ab Ear Canal BNL (EC_BNL) is greater than a predetermined threshold value C_SNR.

25. The earpiece of claim 21, where a value of UCL is derived by calculating a gradient of a slope of an input-output curve of the dynamic compression between an LCL and an MCL part of the curve, and extrapolating this curve to find the corresponding output level for AC_PK.