Abstract: In one embodiment, an apparatus comprises a switching mechanism to switch an input line between a first input voltage and a second input voltage, a pulse generator coupled to the switching mechanism to generate an electronic pulse train at a high frequency in response to the first input voltage and an electronic pulse train at a low frequency in response to the second input voltage, an oscillator circuit coupled to the pulse generator to receive the electronic pulse train, and an ultrasonic transmitter coupled to the oscillator circuit to produce an ultrasonic signal at a frequency that is a function of a frequency of the electronic pulse train.

Abstract: A hybrid acoustic sensor can include a first acoustic sensor, a second acoustic sensor, and a mixer. The first acoustic sensor can generate a first signal to represent acoustic data in a first bandwidth around a first center frequency. The second acoustic sensor can be co-located with the first acoustic sensor, and can generate a second signal to represent the acoustic data in a second bandwidth around a second center frequency. A lower bound of the first bandwidth can be at a lower frequency than a lower bound of the second bandwidth, and a higher bound of the second bandwidth can be at a higher frequency than a higher bound of the first bandwidth. The mixer can combine the first signal and the second signal into a third signal to represent the acoustic data in a third bandwidth from the lower frequency to the higher frequency.