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Re: 24/96

Subject: Re: 24/96
From: "Raimund Specht" <>
Date: Wed, 23 Apr 2003 09:33:09 -0000
--- 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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