Greg,
Can you provide some links to that information? I've read about a dozen pap=
ers and parsed through tons of information over the last few months and hav=
e been unable to find anything like the stuff you found!
Allbests,
Jordan
--- In Gregory O'Drobinak <=
.> wrote:
>
> Very Interesting, Paul! Can we hear some of these recordings?
>
> I followed the previous posted link to the ars.usda.gov site and found a =
mother
> load of good info, i.e., links to papers by Richard Mankin.
> He's done quite a bit of work recording different insects for study and t=
he
> tools vary depending on what insect/environment they were studying. As it=
turns
> out, they used a lowly AT803B lavaliere mic=C2=A0[self-noise =3D ~ 29dBa;=
not very
> amazing!]=C2=A0to study fruit flies, albeit with some DSP post processing=
. Other
> recording devices used were PVDF film, omni mics wired in a differential =
circuit
> to cancel out ambient noise [classic noise-canceling microphone technique=
],
> infrared photocells, accelerometers with charge amplifiers, hydrophones=
=C2=A0and
> geophones.
>
>
> Geophones are interesting transducers since they are quite sensitive to
> vibration. They pick up the vibrations of whatever they are resting upon.=
The
> operating principle is=C2=A0voltage generation=C2=A0by a magnet suspended=
=C2=A0on springs
> within a coil of wire. Vibration [up & down relative to the axis of the u=
nit]
> makes the magnet move=C2=A0and it induces a voltage into the coil. Becaus=
e of the
> mass=C2=A0of the magnet, the frequency starts to roll off steadily=C2=A0a=
bove several
> hundred=C2=A0Hertz, but you can get some nice sounds from them.=C2=A0I ha=
ve been using
> geophones for recording ambient vibration from machines, structures=C2=A0=
and also
> trees, but they have a certain inherent noise level at high gains that ca=
n be
> rolled off with appropriate high pass filters [use your ears!]. The geoph=
ones
> that Mankin likes are the=C2=A0GS-32CT units=C2=A0and here is the link:
> http://www.geospacelp.com/index.php?id=3D29
>
> You can get them mounted in a ruggedized case with a nice long spike that=
can be
> inserted into the ground for picking up underground sounds. I suspect tha=
t there
> are some MEMS accelerometers that might be usable as well, but I have no=
> experience yet with such devices. Also check out the Sanken microphone si=
te --
> they have some interesting products such as the COS-22. They used to make=
a
> special super sensitive microphone for insect recording that appears to b=
e
> something like a wide geophone with a probe coming out of it. See:
> http://www.atscomms.com/Sales/Products/Mics/Sanken/Contact_Mic/contact_mi=
c.html
> I suppose that if you could find one now it would cost a small fortune
>
> Looks like experimentation is still the name of the game, just get some
> transducers and try out some ideas. Check our Mike Rooke's excellent blog=
site
> for some interesting applications of mics and other transducers. Ambient =
noise
> level will always be an issue [try some of those noise-canceling techniqu=
es] and
> bear in mind that the type of preamp needed to get a good quality signal =
may be
> very different from the one inside your field recorder. You may need a mu=
ch
> higher preamp input impedance for certain transducers in order to achieve=
> optimum results.
>
> Happy hunting!
>
> -Greg
>
>
> =C2=A0
>
> ________________________________
> From: Paul Dickinson <>
> To:
> Sent: Wed, January 12, 2011 11:59:34 AM
> Subject: [Nature Recordists] Re: Recording small things
>
> =C2=A0
> David,
>
> I have had very good results using the Telinga EM-23 to record the
> Dermestid beetles at the Field Museum while they stripped animal
> carcasses. Mixed results using a Knowles BU-21771 accelerometer as a
> contact mic to record/amplify a vermicomposting bin. All worked well
> as long as the entire system was running on battery power.
>
> Paul
>
> >
> > I wonder if anyone on list has experience recording very small
> > things, non-singing insects or invertebrates for instance.
> >
> > I suppose using contact microphones would be one solution. If I was
> > going to record them in open air, is it just a matter of getting the
> > microphones really close?
> >
> > David
>
>
>
>
|