Comparison of acoustic monitoring methods

Since 10 years the German Oceanographic Museum uses “click-detectors” for the acoustic detection of toothed whales, especially harbour porpoises. The detectors notice sound impulses, which are transmitted by harbour porpoises for their orientation to capture their attendance. At the moment there are a lot of different detectors which have various acoustic features. COSAMM had the assignment to make a comparison between the different click-detectors which are used for static acoustic monitoring. With the aid of three different sound-exposure-experiments the devices are certificated in their effective detector radius, their data processing, the software and their handling. While doing so there was a close cooperation with SAMBAH.

The aim of this project was to get a representative and comparable result despite using different detectors. Therefore the cost-benefit ratio of the four devices has been proven to find the best device.

The following click-detectors are tested :

• The T-POD (Timing POrpoise Detectors) to get time and duration of the auditory event.
• The C-POD (Cetacean-POrpoise Detectors) to get various parameters, e.g. frequency, number of cycles, amplitude and envelope curve of an auditory event.
• The PCL (Porpoise Click Logger) to get sound pressure and it's duration.
• The A-TAG which is the only one with two hydrophones to show from which direction the the acoustic noise comes.

The comparison of price and performance shows that the C-PODs are the best devices because of their easy handling and good working. The detector range was significantly bigger than the others.

Federal Ministry of Economics and Energy