I'm trying to record owls calls with the AM in the IPX7 case but I'm not getting anything, while I know that they are there calling. Looking at the spectrum it seems that the low frequencies are very weak in my recordings. The case+AM works fine when recording bats. My current assumption is that the case does not play nice with below 1kHz sounds. How do people deal with this problem? Does turning up the gain while filtering high frequency signals do any good, or should I use a different kind of enclosure?
Thanks
Wim van Dam
Solvang, CA
Hi Wim, The case and the acoustic vent does reduce the sensitivity to lower frequency calls somewhat, particularly in the first few hours after closing the case when it is typically slightly over pressured (and the vent bulges slightly). You can improve the signal to noise ratio at lower frequencies by trying a lower sampling rate. This increases the oversampling that is performed so background noise is reduced and the signal should be stronger in comparison. Ziplock bags seem to be almost completely acoustically transparent, but are obviously less robust for deployment in harsher environments or for longer periods. Alex