DAN DUGAN:
> > I've only examined the 3032 at 44.1 sampling rate, but it looks like
>> it's going strong at 20K. Sound Devices publishes the response of
>> their preamps hidden somewhere on their web site, but I can't find it
> > today. As I recall they're good to at least 50K.
I found it:
http://www.sounddevices.com/tech/7series-bandwidth.htm
Looks like 3 dB down is around 100K.
> > Next time I have access to a 722 I'll try a night recording at high
>> sampling rate with 3032s, and slow it down with SoundHack or
> > something. Thanks for the idea.
Bill Rainey:
>That would be very interesting, but some of the higher intensity bats could be
>present in your 44.1 recordings, as their calls include the 16-22
>kHz interval.
>In a sonogram you would see 4 to10+ millisecond tonal pulses at intervals on
>the order of 100-150 ms. These could be nearly constant frequency, but are
>more likely to be declining FM sweeps from above the Nyqvist.
A couple of months ago I recorded Mexican free-tailed bats, and they
had a lot of chatter audible and visible at the top end of the audio
spectrum in my 183s/MD recording.
>As Gianni Pavan pointed out long ago, the antialiasing filters on the Sony
>consumer DATs are quite 'soft'. With a microphone which didn't roll off at 20
>kHz, some bat calls were often aliased down in 48 kHz tape recordings. The
>aliased calls sweep 'the wrong way' for North American temperate zone bats,
>so they're usually easy to recognize by eyeball.
>
>I fail to recall if Gianni (or others?) have reported bench testing the
>antialiasing filters of the 722, but you might have material for a biological
>assessment at 44.1.
I examined the top ends of my three night sessions (the sunrise
sessions had rain noise.) In one, made at the entrance (riparian
foliage), I see a very faint series of clicks centered around 14 KHz,
repeating two or three per second, in strings a few seconds long with
a break and then on again, rather consistently. The hum of
refrigeration compressors from the cafe was quite audible there, so
it could have been something from that. Nothing in the Ben Johnson
Trail silence (conifer forest), and nothing on the Dipsea Trail
(riparian).
-Dan Dugan
________________________________________________________________________
________________________________________________________________________
"Microphones are not ears,
Loudspeakers are not birds,
A listening room is not nature."
Klas Strandberg
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