>I don't want to prolong this discussion any further but I will just
>add that digitisation is a very non-linear process and that sampling
>will generate lower "beat" tones which come out as enharmonic noise >or qu=
antisation noise. A reasonable mic won't do this.
>However, I am a pragmatist and it's the results that count, not the
>theory. Complex sounds like a bird calls, bat social calls or mammal
>squeaks which are far from a sine wave will sound "gravelly" when
>played back at slower speeds.
David,
The effects that you describe might be the quantization noise of poor 8 bit=
time expansion bat detectors. You mentioned that you also used PCMCIA data=
acquisition boards for recording ultrasonic bat sounds. These devices howe=
ver do not have integrated anti-aliasing filters, which can lead to strong =
aliasing effects.
But if you used a high-quality recording system with proper preamplifiers a=
nd anti-aliasing filters, the digital sampling will not introduce any artif=
acts. In fact, it is far better than the ancient analog tape recording tech=
nology.
Listen to my own bat call recordings at http://www.avisoft.com/sounds.htm#b=
ats and http://www.batcalls.com
Some of these recordings were also made by using conventional 8 bit time-ex=
pansion bat detectors with poor preamplifiers and noisy microphones, which =
is indeed audible. But there are also better recordings that were made with=
high-quality 16 bit recording systems.
Best regards,
Raimund
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