Eric Delory wrote : > 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 http://www.ultrasoundgate.com for details. Raimund Specht Avisoft Bioacoustics
