The Ultra Sonar Bat detects objects within a certain range (I set it to about 60cm), and outputs a note within the range of C3 (131Hz) to A6 (1760Hz). It gets a bit unreliable when too close at about 3-4cm, so it continues to make a C3 note at approximately 5cm and under.

Here is a link to the video from my Drive, though it’s only available to those who are logged into their andrew account. And another.