Bat sound analysis
With the time expansion technique the calls are recorded, and the file is displayed for instance 10 times slower. The time-expanded sound is analysed in a computer program and the diagram (sonogram, spectrogram) can be stored as a picture-file.
The spectrograms (frequency curves) below are recorded with a Petterson D240X bat detector, saved in a digital Roland R-05 recorder and analysed with the BatScan 9 computer software.
The spectrogram shows how the frequency changes over time. Yellow and red indicate high sound intensity.
Calls used for Echolocation
Brown long-eared bat (Plecotus auritus)
Barbastelle (Barbastella barbastellus)
The barbastelle typically use a double ecolacation call consisting of a loud call at 36 kHz to 28 kHz and a quieter call at 44 kHz to 29 kHz.
Barbastelle. Sometimes the quieter call type is omitted. Recordet at a woodland edge.
Whiskered bat/ Brandt's bat
It is nearly impossible to discriminate between Brandts bat and whiskered bat. Note the variations between calls