--- In Marty Michener <>
wrote:
> Raimund (and before Walt gets going again):
>
> We have discussed this almost to death previously on this group
for over
> two years.
>
> We who have been using ATRAC 4 to record, very often quiet sounds
nearly
> masked by loud sounds, have been later able to filter out the loud
sounds
> (like the usual rooster crowing near the mic) and have been
pleased to find
> our quiet sounds still there as if recorded by DAT or R-R tape.
So we keep
> doing - using MD.
Marty,
I know some of these discussions on MiniDisk from the journal of the
Wildlife Sound Recording Society (e.g. Vol 8, No 5, spring 1999).
Also, I do not want to argue against the use of MiniDisk for nature
sound recording. Most of the nature sound recordists record for
their own listening pleasure and there is no doubt, that ATRAC is
appropriate for this purpose.
It's also true, that the effects caused by ATRAC are often not
relevant. Other effects might be more critical for spectrographic
analysis (e.g. reverberation and background noise). However, if the
recording conditions are good, the drawbacks of the compression may
become visible in complex sounds. The temporal masking effects occur
on a time scale of a few milliseconds only. If you look at a
spectrogram with a large FFT length (say 1024 or more), the temporal
resolution of this spectrogram would not be appropriate to see these
effects. Imagine you had a soundfile with a sample rate of 22.05
kHz, a FFT size of 1024 and a Hamming window. This configuration
will provide a temporal resolution of 36 milliseconds only (analysis
bandwidth = 28 Hz). Obviously, we would be unable to see the effects
we are looking for. Instead we had to use a much larger analysis
bandwidth. A FFT length of 128 (or zero-padding on larger FFT sizes)
would resolve temporal details down to 4 milliseconds (analysis
bandwidth = 220 Hz). That would be more appropriate and one should
see some distortion in rapidly modulated signals. However, if you
look at smooth whistles, there will be probably no major
degeneration.
Raimund
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