Rob Danielson wrote:
> Hi Sami--
>
> Welcome. Interesting project! One thought others may be able to
> substantiate or refute. One can encounter peculiar distortions when
> recording very hi Hz sources with DAT and MD. I've encountered this
> numerous times when close micing field crickets and grasshoppers with
> flat response mics. The result sounds as if two or more frequencies
> are beating against each other making lower Hz pops and other
> artifacts. I'd consider renting a good mic, an MD recorder and a good
> reel to reel recorder for a day and run some tests. A used, reel to
> reel Nagra might be fairly affordable. Record at the fastest speed,
> 15 ips. The Jukebox 3 is Mp3 right?.. This seems least likely. Rob
> D.
Often those beat frequencies are quite real, and yes they exist. The
individual animals don't call at exactly the same frequency and the beat
frequency is generated between the calls of two animals. In fact I'm not
sure but what this may be a intentional purpose of simultaneous calling.
I see this often with Toads. I think the winner is the one who can call
the longest as when his competitors run out of steam he gets his pure
call out for as long as he can sustain it. A way of weeding out the fit
from the unfit. Those calls are not just entertainment, but fierce
competition for a mate.
I've not seen beat frequencies when recording a single call with
minidisc, only when there are multiple callers. You have to check
carefully as they can be very synchronized if it's a couple of evenly
matched individuals. You can generally pick it out on a higher
resolution sonogram if no other way. And a call at much lower intensity
(from our location) may be what's causing the beat.
I've been editing Toad tracks the last couple weeks, so am way too
familiar with their calls right now. Since all of the editing is being
done with the sonogram rolling, I can say definitively that this is only
real with the toad calls, not a artifact. I've heard the beating in the
field with my own ears without thinking about it, but it was in doing
the editing, where at first you think something is wrong, that I came up
with the above theory. On the level of behavior, I'm going to have to
study it more.
So be careful what you call artifact. (and we have not even got into
multiple reflection paths, which are also a real part of the environment)
Walt
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