I will be monitoring bats with AudioMoths, and in order to determine the range the device can detect wildlife I want to perform an active test in all directions from the device with a speaker (5m, 10m, 15. etc...).
I only have a regular speaker, which is unable to produce sounds at frequencies bats generally produce calls. I was wondering if you have any advice how to, considering this limitation, still perform as reliable a test as possible? How much decibels should the speaker produce? On what frequency (up to +- 16kHz) should I play tones?
Thanks in advance!
Hi Koen, I have several diy devices to playback bat sounds. I like to use ribbon tweeters which have a wide frequency range. I use a fairly cheap 6W model like used in the Vrignault batplayer project. Be aware that the sounds are much weaker that the bats can emit so it is no comparison to test the "range" The range mainly depends on the volume the bet emits, the direction and the emitted frequency. Oh, and you would not want to work on 16kHz where you can hear only a social call and maybe something of the larger species. Al lot of USB soundcards have higher samplerates, up to 384Khz so you can easily play the higher frequencies, but you need to build or modify the amplifier as these usually are not intended for frequenties above 22kHz.