Lang:
I used our own solid-dielectric condenser microphones CM16 (see the left
top-most photo on http://www.ultrasoundgate.com/usg.pdf). Such kind of
microphones are commonly used in high-quality bat detectors. They have a
good sensitivity and a relatively flat frequency response (they may go up to
200 kHz), but require an external polarization voltage of about 200V.
You are correct, the echoes and the reverberation are the calls reflected of
the walls of the house (there is some kind of niche). This is the view from
my balcony where I placed the microphones:
http://www.avisoft-saslab.com/sounds/stereo/balcony.jpg. The wall on the
right seems to be responsible for the strong echoes.
Yes, your SongFinder Plus seems to be a useful unit for binaural listening
to lower-pitched bat calls. I also don't know of any similar device.
Raimund
> Raimund:
>
> Awesome! What kind of microphones did you use? And what accounts for the
> echo/reverberation that I hear especially to one side? Is this the calls
> reflecting off a hard surface?
>
> Lang
>
> p.s. My SongFinder Plus has a heterodyne mode that currently extends to 40
> kHz. I can hear a number of bat sounds with the unit. The headset is
> binaural, so I can look in the direction of an incoming bat and then see
> if
> fly by in the twilight. Right now I believe it's the only device that
> allows
> a person to hear bats in real time binaural.
>
> http://www.naturesound.com/songfinder/plus.html
>
> Hi,
>
> I just want to share some of the stereo bat sound recordings that I made
> >from my balcony last night.
>
> I used a sound activated PC-based recording set-up that registered all bat
> passings during the night. Here are some of these recordings (European
> Common Pipistrelle, Pipistrellus pipistrellus):
>
> http://www.avisoft-saslab.com/sounds/stereo/pipistrelle1.mp3 (both
> echolocation and social calls, 326KB)
>
> http://www.avisoft-saslab.com/sounds/stereo/pipistrelle2.mp3 (echolocation
> calls, 173KB)
>
> http://www.avisoft-saslab.com/sounds/stereo/pipistrelle3.mp3 (echolocation
> calls, 1186KB)
>
> The two ultrasound microphones where placed close together (about 2
> inches).
> The angle between them was about 30 degree (these microphones are
> relatively
> directional). There is a wall in front of my balcony that produced the
> strong echoes on the right channel.
>
> The initial sample rate was 250 kHz (recorded using Avisoft-UltraSoundGate
> 416). I have then set the sample rate in the file headers to 11.025 kHz,
> which provides a time-expansion factor of about 22.
>
> Regards,
> Raimund Specht
>
>
>
>
> [Non-text portions of this message have been removed]
>
>
>
>
> "Microphones are not ears,
> Loudspeakers are not birds,
> A listening room is not nature."
> Klas Strandberg
> Yahoo! Groups Links
>
>
>
>
>
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