> About silence, just recently I had a wonderful experience in the abandone=
d
> tunnels (a 12 km network) of a chalk cave. Absolute silence improved by
> soft sound absorbing chalk powder and very irregular tunnel surfaces. Nex=
t
> time I go there with my microphones and recorders for doing some tests. I=
n
> some larger tunnels we found bats colonies, their social calls were
> fascinating, but the most impressive noise was those of the wings of the
> bats flying when disturbed. I did some recording with a phonometer but it=
s
> noise floor was higher than the ambience noise, probably I'd need the GRA=
S
> microphone to make measures there.
> Next time I'll go there with my usual microphones and recorders for doing
> some recordings.
Gianni,
This afternoon I was back with the bat roost I have been monitoring with IR=
cameras and ultrasound for some time. Try to get hold of a cheap heterodyne=
bat detector to hear all the ultrasounds you are missing. It's a whole new=
world of sound.
These bats are a maternity roost of Lesser Horseshoe bats, and they are
surprisingly active in the daytime in a dark loft space. More fun will come=
later as the youngsters learn to fly.
It's not just bats that you can hear with a detector, but many insects and=
small mammals also emit ultrasound.
David Brinicombe
|