Abstract: A method for determining a displacement offset of a voice coil of a speaker, comprising: providing a drive signal comprised of a program content signal and a test signal to the voice coil of the speaker; determining at least one value representative of an impedance of the voice coil according to a voice coil voltage and a voice coil current, wherein the voice coil voltage and the voice coil current result from, at least, the test signal; determining whether the at least one value indicates that an offset displacement of the voice coil exceeds a predetermined offset distance; and reducing a magnitude of the drive signal provided to the voice coil if the at least one value indicates that the offset displacement of the voice coil exceeds the predetermined offset threshold.

Abstract: An earphone includes a loudspeaker, a microphone, a housing supporting the loudspeaker and microphone, and an ear tip surrounding the housing and configured to acoustically couple both the loudspeaker and the microphone to an ear canal of a user, and to acoustically close the entrance to the user's ear canal. A processor receives input audio signals from the microphone, detects peaks having a frequency of around 1 Hz in the input audio signals, based on the detected peaks, computes an instantaneous heart rate, measures a frequency of an oscillation within the instantaneous heart rate, and based on the frequency of the oscillation, computes a rate of respiration.

Abstract: An acoustic pressure reducer acoustically couples to and provides acoustic impedance to attenuate the acoustic box pressure of an acoustic system, such as a loudspeaker system. The pressure reducer may also allow an ambient pressure of the acoustic system to equalize with an ambient pressure of an external environment and the ambient pressure of the acoustic pressure reducer at a certain rate. The attenuation may allow for inexpensive acoustic sensors to be utilized within the pressure reducer to measure one or more acoustic properties of an attenuated acoustic pressure within the pressure reducer. An unattenuated acoustic pressure value of the acoustic system may be estimated using a known transfer function of the pressure reducer and the attenuated acoustic pressure values measured within. A controller coupled to the acoustic system may adjust one or more operating characteristics in response to estimating the unattenuated acoustic pressure.

Abstract: An earphone includes a loudspeaker, a microphone, a housing supporting the loudspeaker and microphone, and an ear tip surrounding the housing and configured to acoustically couple both the loudspeaker and the microphone to an ear canal of a user, and to acoustically close the entrance to the user's ear canal. A processor receives input audio signals from the microphone, detects peaks having a frequency of around 1 Hz in the input audio signals, based on the detected peaks, computes an instantaneous heart rate, measures a frequency of an oscillation within the instantaneous heart rate, and based on the frequency of the oscillation, computes a rate of respiration.

Abstract: An acoustic pressure reducer acoustically couples to and provides acoustic impedance to attenuate the acoustic box pressure of an acoustic system, such as a loudspeaker system. The pressure reducer may also allow an ambient pressure of the acoustic system to equalize with an ambient pressure of an external environment and the ambient pressure of the acoustic pressure reducer at a certain rate. The attenuation may allow for inexpensive acoustic sensors to be utilized within the pressure reducer to measure one or more acoustic properties of an attenuated acoustic pressure within the pressure reducer. An unattenuated acoustic pressure value of the acoustic system may be estimated using a known transfer function of the pressure reducer and the attenuated acoustic pressure values measured within. A controller coupled to the acoustic system may adjust one or more operating characteristics in response to estimating the unattenuated acoustic pressure.