a sonogram is more descriptively called a sound spectrogram. It plots the sounds frequency against time.

Sonograms of bat echolocation calls are made from time expansion recordings. The whole of the bat sound is recorded and replayed at a slower rate. This results in the frequency also to be much lower. This can then be heard by us with the advantage that the entire structure of the call can be heard and studied in its original form. (see also bat detector)

Example of a FM (Frequency Modulated) call.
N. noctula sonogram 1 (feeding buzz)
N. noctula sonogram 2

Example of a CF (Constant Frequency) call.
R. ferrumequinum sonogram 1
R. ferrumequinum sonogram 2

Recordings courtesy of:
Bat Ecology & Bioacoustic Laboratory
School of Biological Sciences
University of Bristol

Microphone: Ultrasound Advice S-25
Recording Type: Time Expanded (10X)
Digitisation Rate: 44.1 kHz (441 effective), 16 bit.

Alternative forms for sonogram : sonograms, spectrogram.