UltraVox is primarily designed to monitor ultrasonic vocalizations of rodents, but it can also handle animal calls of any other nature (even subsonic sound, e.g. as produced by elephants and whales) and human speech.
UltraVox converts speech and calls to onset and offset times, just like it does with ultrasound. Automatic monitoring of audible sounds requires the use of a standard microphone instead of an ultrasound detector.
The monitoring of subsonic sound requires the use of a special microphone, which is sensitive to low-frequency sound, and a custom-made audio filter with a specific bandwidth (for example 0-50 Hz).