> I've come through an excellent audio acquisition board,
> famous brand, with 96kHz SR & 24 bit resolution,
> and was astonished that the device was actually cutting
> at 20 kHz....
Yes, I have seen such effects in other models too. Besides
the cutting at 20 kHz other models may exhibit unacceptable
inherent noise levels at ultrasonic frequencies. Similar effects
can also be found in the playback paths of some of the new
96 or 192 kHz soundcards.
Therefore, Avisoft Bioacoustics has designed various
dedicated A/D conversion units for recording animal
ultrasounds. These devices employ A/D converters
that work reliably up to half the sampling frequency. In
contrast to the National Instruments data acquisition boards,
these USB-based devices do not require specialized recording
software because they appear to the PC as standard
soundcards. Therefore, any audio recording software
(e.g. CoolEdit) that allows to enter the higher sampling
rates (192, 250, 500 or 750 kHz) can be used.
A dedicated interface box for connecting hydrophones is
currently under construction.
See <a href="http://www.ultrasoundgate.com";
rel="nofollow">http://www.ultrasoundgate.com</a> for details.
Raimund Specht
Avisoft Bioacoustics
|