Archived from groups: rec.audio.tech (
More info?)
"Dick Pierce" <dpierce@cartchunk.org> wrote in message
news:dc02c02f.0405120623.552b6c55@posting.google.com...
> "Jukka Andersson" <jukka.andersson@remove.rihmasto.com> wrote in message
news:<Tpmoc.146$xa5.109@read3.inet.fi>...
> > "Geoff Wood" <geoff@paf.co.nz-nospam> wrote in message
> > news:%Eaoc.1334$FN.150423@news02.tsnz.net...
> > > Jukka Andersson wrote:
> > > > Is there easy solution to make a ultrasound receiver for analog
mixer
> > > > that accepts up to 40KHz
> > > > quite nicely.? (tested with oscillator)...
> > > >
> > > > not actually underwater but it would be nice bonus..
> > > >
> > > > just would like to make few experiment with 24bit/96KHz and slow
> > > > things down to human ear range.
> > >
> > >
> > > Get a Tannoy Supertweeter.
> > >
> > > You may not be able to hear much (any) different, but it'll keep the
bats
> > > away.
> > well i need to record those bats , not make them fly away
> > something like microphone made of piezo would do it?
>
> Generally, no. Piezos work as "well" as they do because they have
> a few conveniently placed bending resonant modes. That means they
> are pretty narrow-band devices with horrible frequency response.
> It works for sonar, because sonar broadcasts and receives at
> these same frequencies. Hydrophones aren't usually piezo: they're
> more conventional dynamic or electrostatic microphones that are
> consructed for in-fluid use. Often a hydrophone is a fairly conventional
> audio microphone that's immersed in something like castor or silicone
> oils.
>
> Also, for recording signals at the sorts of frequencies you're talking
> about, the micriphone has to be physically SMALL. If you're recording
> air-borne acoustical phenomena at 40 kHz, you're talking diaphragm
> sizes in the realm of 1/4". Hydrophone receivers at those sorts of
> frequencies can be physically larger because the speed of sound in water
> is faster than in air (1480-1500 m/s in water vs 344 m/s in air), and
> thus the diaphragm size can be corresondingly larger (1" vs 1/4").
>
> So, unless you know that whant you want to record is at one of the
> resonant frequencies of your piezo, or you don't care how bad the
> result is, then, no, piezos make lousy microphones.
hmm....
sadness raises..
well I need low cost solution to archive lo-fi quality sounds from 20khz ->
40khz
its what my A/D converter does understand with only little drop of gain...
now what device should I place next to mixer?
lets say I would like to record normal electronic devices and nature and
other things
that does exist in 20-40khz range. dont really care if the sound does sound
coloured since
I will anyway slow it down to lets say 2-4 times to bring it in our hearing
range.
..jukka
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