Speaker impedance monitoring

• US 9,635,480 B2
• Filed: 06/28/2016
• Issued: 04/25/2017
• Est. Priority Date: 03/15/2013
• Status: Active Grant

• Current Assignee: Cirrus Logic Incorporated
• Original Assignee: Cirrus Logic Incorporated
• Inventors: Miller, Antonio John, Su, Jie
• Primary Examiner(s): HUBER, PAUL W
• Application Number:
  US15/195,785
• Publication Number:
  US 20160309270A1
• Time in Patent Office: 301 Days
• Field of Search: None
• CPC Class Codes: G06F 3/165 Management of the audio stream, e.g. setting of volume, audio stream path
• CPC Class Codes: H04R 2410/05 Noise reduction with a separate noise microphone
• CPC Class Codes: H04R 2460/01 Hearing devices using active noise cancellation
• CPC Class Codes: H04R 2499/11 Transducers incorporated or for use in hand-held devices, e.g. mobile phones, PDA's, camera's
• CPC Class Codes: H04R 29/001 for loudspeakers H04R29/007 takes precedence
• CPC Class Codes: H04R 3/00 Circuits for transducers , loudspeakers or microphones
• CPC Class Codes: H04R 3/005 for combining the signals of two or more microphones specially adapted for hearing aids H04R25/407

Abstract

A speaker impedance may be determined by monitoring a voltage and/or current of the speaker. The calculated impedance may be used to determine whether the mobile device containing the speaker is on- or off-ear. The impedance determination may be assisted by applying a test tone low level signal to the speaker. The test tone may be inaudible to the user, but used to determine an impedance of the speaker at the frequency of the test tone. The impedance at that test tone may be used to determine whether a resonance frequency of the speaker is at a frequency corresponding to an on- or off-ear condition. The measured speaker impedance may be provided as feedback to an adaptive noise cancellation (ANC) algorithm to adjust the output at the speaker. For example, when the mobile device is removed from the user'"'"'s ear, the ANC algorithm may be disabled.

Claims

1. A method, comprising:

outputting, by a processor, a test tone to a speaker at a first frequency;

receiving, by the processor, at least one of a voltage measurement and a current measurement for a speaker after outputting the test tone;

calculating, by the processor, an impedance of the speaker at the first frequency based, at least in part, on the received at least one of a voltage measurement and a current measurement; and

detecting, by the processor based at least in part on the calculated impedance, when the speaker is removed from an ear of a user by determining that the calculated impedance at the first frequency is above a threshold impedance level.

2. The method of claim 1, wherein the received at least one of a voltage measurement and a current measurement comprises both a voltage measurement and a current measurement, and wherein the step of calculating the impedance of the speaker comprises:

applying a bandpass filter to the voltage measurement and the current measurement, wherein the bandpass filter is centered at the first frequency of the test tone;

applying a low pass filter to the result of bandpass filtering the voltage measurement and the current measurement; and

dividing the result of the low pass filtering of the bandpass filtered voltage measurement by the result of the low pass filtering of the bandpass filtered current measurement.

3. The method of claim 1, wherein the step of detecting when the speaker is removed from the ear of the user comprises determining a change in an impedance curve of the speaker based, at least in part, on the received at least one of a voltage measurement and a current measurement.

4. The method of claim 1, further comprising adjusting an adaptive noise cancellation (ANC) algorithm based, at least in part, on the calculated impedance.

5. The method of claim 4, wherein the step of adjusting the adaptive noise cancellation (ANC) algorithm comprises disabling the adaptive noise cancellation (ANC) algorithm when the speaker is detected as removed from the ear of the user.

6. The method of claim 1, wherein the step of determining that the calculated impedance at the first frequency is above a threshold impedance level comprises determining a change in a resonance frequency of the speaker that indicates the speaker is removed from the ear of the user.

7. The method of claim 1, wherein the step of calculating the impedance of the speaker comprises applying one or more filters to the received at least one of a voltage measurement and a current measurement for the speaker.

8. The method of claim 1, further comprising turning off a display screen of a device comprising the speaker when the speaker is detected as removed from the ear of the user.

9. An apparatus, comprising:

a speaker;

an amplifier coupled to the speaker;

a processor coupled to the amplifier, in which the processor is configured to execute steps comprising;

outputting a test tone to the speaker at a first frequency;

receiving at least one of a voltage measurement and a current measurement for the speaker during output of audio by the speaker;

calculating an impedance of the speaker at the first frequency based, at least in part, on the received at least one of a voltage measurement and a current measurement; and

detecting, based at least in part on the calculated impedance, when the speaker is removed from an ear of a user by determining that the calculated impedance at the first frequency is above a threshold impedance.

10. The apparatus of claim 9, wherein the received at least one of a voltage measurement and a current measurement comprises both a voltage measurement and a current measurement, and wherein the step of calculating the impedance of the speaker comprises:

applying a bandpass filter to the voltage measurement and the current measurement, wherein the bandpass filter is centered at the first frequency of the test tone;

applying a low pass filter to the result of bandpass filtering the voltage measurement and the current measurement; and

dividing the result of the low pass filtering of the bandpass filtered voltage measurement by the result of the low pass filtering of the bandpass filtered current measurement.

11. The apparatus of claim 9, wherein the step of detecting when the speaker is removed from the ear of the user comprises determining a change in an impedance curve of the speaker based, at least in part, on the received at least one of a voltage measurement and a current measurement.

12. The apparatus of claim 9, wherein the processor is further configured to perform steps comprising adjusting an adaptive noise cancellation (ANC) algorithm based, at least in part, on the calculated impedance.

13. The apparatus of claim 12, wherein the step of adjusting the adaptive noise cancellation (ANC) algorithm comprises disabling the adaptive noise cancellation (ANC) algorithm when the speaker is detected as removed from the ear of the user.

14. The apparatus of claim 9, in which the apparatus is a mobile device.

15. The apparatus of claim 9, wherein the step of determining that the calculated impedance at the first frequency is above a threshold impedance level comprises determining a change in a resonance frequency of the speaker that indicates the speaker is removed from the ear of the user.

16. The apparatus of claim 9, wherein the step of calculating the impedance of the speaker comprises applying one or more filters to the received at least one of a voltage measurement and a current measurement for the speaker.

17. The apparatus of claim 9, further comprising a display screen coupled to the processor, wherein the processor is further configured to perform steps comprising turning off a display screen of a device comprising the speaker when the speaker is detected as removed from the ear of the user.

18. A computer program product, comprising:

a non-transitory computer readable medium comprising code to execute the steps comprising;

outputting a test tone to a speaker at a first frequency;

receiving at least one of a voltage measurement and a current measurement from a speaker during output of audio by the speaker;

calculating an impedance of the speaker at the first frequency based, at least in part, on the received at least one of a voltage measurement and a current measurement; and

detecting, based at least in part on the calculated impedance, when the speaker is removed from an ear of a user by determining that the calculated impedance at the first frequency is above a threshold impedance level.

19. The computer program product of claim 18, wherein the step of calculating the impedance of the speaker comprises:

applying a bandpass filter to the received at least one of a voltage measurement and a current measurement, wherein the bandpass filter is centered at the first frequency of the test tone;

applying a low pass filter to the result of bandpass filtering the voltage measurement and the current measurement; and

dividing the result of the low pass filtering of the bandpass filtered voltage measurement by the result of the low pass filtering of the bandpass filtered current measurement.

20. The computer program product of claim 18, wherein the step of detecting when the speaker is removed from the ear of the user comprises determining a change in an impedance curve of the speaker based, at least in part, on the received at least one of a voltage measurement and a current measurement.