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Pub. No.:    WO/2018/004547    International Application No.:    PCT/US2016/039888
Publication Date: Fri Jan 05 00:59:59 CET 2018 International Filing Date: Wed Jun 29 01:59:59 CEST 2016
IPC: H04R 3/00
Applicants: CIRRUS LOGIC, INC.
MILLER, Antonio, John
SU, Jie
Inventors: MILLER, Antonio, John
SU, Jie
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.