The image above is a plot of a small brown bat call recorded using our Belfry Bat Detector and a laptop PC with soundcard. You can see the quite noticeable "feeding buzz" occur just before the 5th second. The software used to record this bat call is free shareware and can be downloaded from http://www.visualizationsoftware.com/gram.html and works extremely well.

Please keep in mind that the frequency markings on the left (vertical axis) should be multiplied by a factor of 16 to ascertain the true frequency. What we see on the graph above is the bat call AFTER it has been converted to the human hearing range.

If you capture a known bat call species using a Belfry Bat Detector and the Spectrogram program, I would appreciate an email with a copy of the sound file as we are building a global bat call library that we can share with other customers.