> Walter Knapp wrote:
> (snip)
> I wonder if anyone records anything above 10 khz?
Now there's a challenge! And there I was the other evening engrossed in
recording the lowest possible rumblings of distant thunder in stereo and
with all the low cut filters turned off, then a bat circled directly
overhead giving loud, high pitched 'pink-pink-pink' calls. The contrast of
sounds was wonderful, especially in stereo. When I later analyzed the bat
calls they began at 10.5 kHz and extended up to 15 kHz. The growling
thunder was mostly below 250 Hz.
I am lucky to have good high frequency hearing still, so I do sometimes
record high pitched insects because they make such interesting sounds, and
they are part of my world. Two of my local cicada species call at around 11
kHz. I think one of them is actually 13 kHz but I need to double check
that.
I record with DAT but I'm sure if MD had been available when I started to
get serious about recording, I would have gone for MD because they are so
lightweight and batteries last forever - ideal for backpacking, and very
importantly, MD is a lot cheaper than DAT. The issue of how long the DAT
tapes might last is not really relevant because it is now quite easy to
transfer digital recordings to a more permanent medium e.g. CD.
My understanding is that while MD is just great for relatively pure sounds
below, say, 10 kHz it is not so suitable for accurately recording the high
pitched and raspy sounds of insects? Is that the main difference
science-wise between DAT and MD? I can definitely hear a difference,
because MD takes out those tiny additional clues whereby one positions
oneself aurally within the landscape - DAT retains that "breathing space"
while MD creates more of a vacuum, a more 'perfect' world. Maybe because we
are so used to turning off our ears due of noise pollution, we are less
aware of those tiny aural clues that give shape to the landscape - that
expectant "atmosphere" that happens between bouts of birdsong or frog calls.
Maybe people who live very close to nature are more aware of those sorts of
"irrelevant" sounds, and use them even to survive.
But the main thing is that people are out there recording wildlife sounds,
whatever their equipment! We are so lucky to have access to high quality,
portable recording equipment, DAT, MD and whatever. They are all excellent.
The pity of it is that such equipment did not exist in those eras when
natural soundscapes were unpolluted.
Vicki Powys
Australia
> richpeet wrote:
>>
>> OK, here is a couple examples to look at and listen to.
>> This is not a hhb. This is a true consumer level Sony MZ R90 Minidisk
>> with a $340.00 Sennheiser ME 62 placed inside of a priceless 32"
>> polyC dish. No edits at all, no filters at all.
>>
>> First is a Warbler and you can see the harmonics do go above 20 khz.
>> This was recorded at about 30'. You can also see from the noise line
>> the compression did cut out very low volume background noise that
>> you, as a person, had no chance of hearing but maybe your dog could.
>
> You should note, before you believe those "harmonics" that go above 20
> khz, that the math done to generate sonograms generates it's own false
> "harmonics". These usually appear off the loudest sounds. Your stuff
> above 20 khz is likely that. Though I can't be sure.
>
> And the math involved is way above my head, so that's about as far as I
> can go on that. Just don't have faith in everything you see in a
> sonogram. It's tough when our very analysis tools flim flam us.
>
> I have noticed the cutoff and this appears to be real. As I've noted,
> this is in a range for which any sensitive work should move up to 96 khz
> sampling rates. And it's cutting off sounds that are more than 50db
> below the dominant sounds by my measurement with my sonogram software.
> My bet is if you isolate what it cut off up there you will find it all
> to be mic hiss and such like.
>
>> Second is a Golden-crowned Kinglet recorded about 175' distant. About
>> the highest pitched bird in a pure tone that I have recorded. You can
>> see it was recorded at low volume and it is all there.
>
> I wonder if anyone records anything above 10 khz? I'm not a bird
> recordist, and my frogs top out at 8 khz. About the same level as the
> Kinglet. Though they don't modulate the frequency as much as the kinglet
> seems to be doing. Theirs are precise bursts of intense sound all at the
> same frequency range. You can see that sono here:
> http://wwknapp.home.mindspring.com/Sonograms/Little.Grass.Frog.Sono.jpg
> Note that the sono is of a sound carefully worked over to give a clear
> sono display to show the call. Primarily by doing sound intensity
> filtering to drop the quieter stuff. I'm pretty sure the echo's at very
> low frequency are another math problem.
>
> Walt
>
>
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