Do you use particular microphone? Which set up do you use? Could you advise me some scientific paper or book?
There are many websites about bat detectors and bats sound recorders. In general to precisely measure all parameters of bats signals (SPL, full bandwidth) is better to use professional microphone (B&K, G.R.A.S) and high speed DAC (min. 16 bits, 500 kHz sampling rate). The main problem of the bat recorders is the microphone and its limited sensivity and non-flat frequency response. Generally to choose adequate method You have to decide what You want to measure or what parameters would You like to extract from a recorded signal. Try to google: Avisoft, Petterssen, Widelife Acoustics, Anabat, Lunabat - they manufacture bat recorders and as for the methods used You can find something googling: zero crossing, time-expansion, heterodyne, divider bat detectors. I hope this will help You
Dear All,
in fact heterodyne based bat detectors are popular an useful. The problem with, in my opinion, all bat detectors which make sound audiable is in fact that You have to train Your ear with bats sounds. The trend to have recordings on SD card makes sense because You eliminate:
- processing of sound (heterodyning, time-dividing) to make it audiable what affects the orginal signal,
- not real time recodings (time-expansion systems are not real time).
Of course the amount of data is enormous (1GB ~40 min of recording). Since the signals vary along species You can extract some features what gives You opportunity to determine species/genus. There are even some methods to automeaicly classify the extracted parameters and suggest You the most probable answer. Maybe the next generation of bat detectors will operate this way.
Since I am a sound engineer in a field of ultrasound bat detectors have very poor microphones and the consequence of this fact is that having 2 different bat detectors You will have two different not comparable results. I think that it was a reason why in USA only ANABAT on wind farms are used. Maybe ANABAT is not the best bat detector but this way they have comparable results.
I use a full spectrum SD recorder of Animal Sound Labs (lunabat.pl) recently to records whales and penguins.
Best regards from antarctic
Chris
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