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Ultra sound (was MS...)

Subject: Ultra sound (was MS...)
From: "Steve Pelikan" pelikan45224
Date: Mon Oct 13, 2008 8:43 pm ((PDT))
Kevin et. al.

This is a matter I've been interested in recently, so I'll make a
couple assertions by way of query (meaning I'm happy for any
corrections and instruction anyone can offer).

1) The new series MKH mics are reportedly fairly flat up to 50 (or 60)
KHz. Other manufacturers (Earthworks, for example) make microphones
that also respond well up to 50 kHz or so.

2) The SD 702 (and so, I guess the 722 etc. as well as other modern
devices) can sample stereo at 96 kHz (and maybe even 192?) But even at
96 kHz, this is enough to digitize signals up to 48 kHz.

3) Some species of bats (like Big Brown (Eptesicus) and Hoary
(Lasiuris)) have most of their echo location calls in the under 40 kHz
range (Big Browns in the eastern US center at 28 kHz) and so could be
recorded with an MKH-SD set up. Other bats (Myotis sp. for example)
use higher frequencies ( perhaps even 70 kHz+ ?) and so would be
beyond the range of this sort of recording set up. There's special
equipment that works for these subjects.

4) Air has a very high impedance at these sorts of frequencies and so
close proximity and/or a parabola type device will be important for
decent recordings.

5) Insects typically produce sounds covering a wide frequency range
(like jangling coins or keys) but are typically represented in our
hearing range as well as ultrasonically. Are there many examples of
insects whose sounds are _exclusively_ ultrasonic? (The one example
I've read is some Arctuid moths make ultrasonic clicks thought to be
useful in "jamming" bat's sonar --- I'd love to hear that recorded!).

6) As far as experiencing/playing back high Hz recordings one can a)
draw spectrographs and try to be happy with them b) slow down the
playback c) use some sub-sampling scheme to reduce the frequency of
the samples or d) use some transform or heterodyne technique to focus
on a specific frequency range and make it audible. What do any of
these methods (c&d) do to phase information?

I'd be happy to hear what anyone can tell me about any of these topics!

Steve P


--- In  Kevin Colver <> wrote:
>
> The SD 722 records from 10 Hz to 40 kHz.  Do you just slow it or drop =

> frequency on your computer to hear them?  Our ears only go up to 20
> kHz and mine are probably lower than that by a fair amount.
>
> Kevin
>
> On Oct 12, 2008, at 9:29 PM, Martyn Stewart wrote:
>
> > Kevin, if you record at a higher sample and bit rate with the 800
> > series you can get many good sounding bugs and even bat recordings
> > with the higher frequencies.
> > Many insects call in the higher frequencies...
> >
> > Martyn
> > *************************************
> > Martyn Stewart
> > http://www.naturesound.org
> >
> > Redmond WA
> > 425-898-0462
> >
> > Make every garden a wildlife habitat
> > **************************************
> > Listen to the Birds and the Bees at
> > http://naturesound.libsyn.org/
> > ------------------------------------------------
> > View a Nature Recordists Blog!
> >
> > http://naturesound.blogspot.com/
> >
> > http://naturesound.org/Copyright.html
> >
> > On Oct 12, 2008, at 7:08 PM, Kevin Colver wrote:
> >
> > > I notice the specs on the MKH 800 show a frequency response of 30 Hz
> > > - 50 kHz. Does the drop off at 30 Hz ever seem a problem? I know
> > > that in the modern world I usually want to rid my recordings of low
> > > frequency intrusions - but not always. Also, how does the frequency
> > > response well above the 20 kHz upper limit that the SD722 can
> > achieve
> > > come into play? Is the extra 30 kHz range on the high end useful?
> > >
> > > Kevin
> > >
> > >
> > >
> > >
> >
> >
> >
> >
>
>
>
>





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