Vicki Powys wrote:
> There must be something in this compression argument, especially for the
> sorts of sounds that Rich Peet describes as "fast attack sounds". For th=
e
> first time I have noticed a difference, not between MD and DAT, but simpl=
y
> between the 48 kHz recording rate of my Sony Pro DAT and the 44.1 kHz
> CD-compatible rate that my computer uses.
>
> My DAT records at 48 kHz so I need to convert this to 44.1 kHz in order t=
o
> process the sounds on my computer. To do the conversion I simply feed th=
e
> sounds from the DAT to my iMac via analogue inputs, where the sound is
> automatically taken up by the computer at 44.1 kHz. Up till now I've not
> noticed any difference in sound quality between sounds heard directly fro=
m
> the DAT compared to the same sound once it has been fed into in the
> computer.=20
>
> But there is a particular species of frog here in Australia, the Striped
> Marsh Frog (Limnodynastes peronii) that gives a loud 'tok' call, a bit li=
ke
> the sound of a tennis ball being hit. I have a nice stereo recording of
> these frogs, tok-ing away happily, and it sounds great on the DAT, each t=
ok
> has a beginning a middle and an end, even if such a short note. But when
> reduced to 44.1, the call is less pleasing and rather sharper, and better
> listened to at a lower volume. There isn't a lot of difference, but you =
can
> hear it.=20
>
> I thought it worthwhile to report on this perceived effect. Perhaps the
> Striped Marsh Frog would make a good 'test subject' for further compressi=
on
> tests!
This is a sample rate conversion problem, may not even be inherent in
the 44.1 khz rate. More likely it's the particular programming the iMac
is using to do the conversion.
I have a couple recordings of the same frog recorded by David Stewart.
It's on CD, so 44.1khz sampling rate. The individual calls have the
clear beginning, middle, end you describe, though as you say it's a very
brief call. I'm, of course not sure of the difference you describe, so
cannot say which type of sound experience it is.
It would be a great leap to think that compression is going to have the
same effects as sample rate conversion, or mess up on the same things.
Two quite different processes. It is a even greater leap of blind faith
than thinking that two different kinds of compression will have such
similar effects that one can be analyzed to determine what another will
do. And the latter is way outside the pale for scientific analysis.
One should also realize that the idea that fast attack sounds will not
work with compression is one proposed by folks who thought it up without
being experienced over time with actual field use of compression. It is
very simplistic and not at all accurate in any kind of universal way.
Sometimes this can happen, but it's far from universal, especially when
dealing with actual natural sounds as opposed to custom made sounds.
We record with systems, folks, I repeat that the major errors in our
recordings compared to the actual call by the animal at the animal are
due to the environment, our technique and our microphones. Not our
recorders. Do not be fooled into thinking that any recording system is
getting it right in the sense of that actual call. It's getting
something that resembles the call. And then we process the sound,
changing it even more. And then play it with sound reproduction systems
that are often barely removed from junk. And analyze it with analysis
methods that have their own built in and not entirely predictable errors.
Walt
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