Patent attributes
Ultrasonic audio processing circuitry and a method useful in ultrasonic presence detection. An ultrasonic burst generator produces an ultrasonic burst signal at one or more ultrasonic frequencies, and an equalizer equalizes that ultrasonic burst signal according to frequency response characteristics of the speaker and microphone at those ultrasonic frequencies. Driver circuitry drives a speaker with the ultrasonic burst signal, which may be combined with an audible audio signal. An ultrasonic separation filter separates an ultrasonic portion from a signal received at a microphone, and processing circuitry is provided to determine a delay time of an echo corresponding to the ultrasonic burst signal in that separated ultrasonic portion of the received signal. In another aspect, the equalizer equalizes an ultrasonic portion of the signal received at a microphone, according to frequency response characteristics of the speaker and microphone at the ultrasonic frequencies of the burst.
