Speaker impedance monitoring

摘要

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.

主权项

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.