Dear Susan
I think the best option is to set a PC based recording system. It is
flexible, programmable, and a lot cheaper than stand-alone recorders.
We developed a software to record simultaneously and continuously up
to 48 channels in a single multichannel file. We could easily adapt
it to record individual files when the signal is above a threshold.
Otherwise you could run several instances of our sound spectrograph;
in such a case each copy of the software records a timestamped stereo
file everytime in one of the two channels there is signal above a
threshold in a specific frequency band.
In case all 50 crickets will sing together I'm not sure a single pc
will be able to record to disk 25 stereo files at the same time; in
such a case it could be safer to split the task on 2 or more separate
low cost PCs.
We worked well with multiple MOTU firewire interfaces: for example
the HD896 costs less than 1500$ (verify in US) and provides 8
channels with very good mic preamplifiers with 96kHz sampling. If you
need to spend less, the PRESONUS FIREPOD offer similar features for
600$ (verify in US). By using PCI multichannel boards such as the
MAUDIO 1010 you could further halve the cost but then you need to add
external microphone preamplifiers.
Otherwise you could use a software made by an italian company with
our cooperation that allows to setup a network (100mbit or 1Gbit)
with multiple PCs each one equipped with sound boards. Each PC is a
"sender" connected to a "director" PC that receives through the
network the data streams coming from all the sound boards installed
in the "senders"; the director allows to connect each channel from
"senders" to "recorders" , logical devices on the "director" PC that
can be programmed to record a file each time the signal of a channel
goes beyond a threshold in a specified frequency range (in the future
version it will be possible to setup an autoadaptative threshold that
takes into account slow variations of the background noise).
Recorded files have a timestamp in the filename and the name of the
sender/channel.
You may use, say, 8 PCs each one with an 8 channel sound board to
feed 64 individual recorders on the "director" PC.
But you can also use less PCs with more sound boards each.
Probably, with 32 or 48 kHz sampling, you can also concentrate
everything on a single PC with multiple disks on which to distribute
the channels to be recorded (recording 64 channels together in a
single file is easy, recording 64 independent files on the same disk
is more difficult).
Mics could be cheap but good condenser microphones with P48 powering
that may cost about 30$ each (I think at Behringer C2). You may spend
a lot less if you build your own condenser mics with capsules such as
the Primo model 158.
Gianni Pavan
--------------------------------------------------------------
Gianni Pavan
Centro Interdisciplinare di Bioacustica e Ricerche Ambientali
Universita' degli Studi di Pavia
Via Taramelli 24, 27100 PAVIA, ITALIA
Tel +39-0382-987874
Fax +39-02-700-32921
Web http://www.unipv.it/cibra
Email
|