I thought two notes could be added to the suggestions made about hard- and software audio recording machines for bioacoustics, now that digital audio is beating records at attractive prices.
Watch out.
1) On the hardware side:
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 20kHz. High end audio systems like the previously mentioned Pro Tools Digi 002 have specs only until 20kHz (see www.protools.com) , above which nothing is guaranteed and I would not bet that they don't filter above 20kHz too to secure dynamic range and only use the high SR to reduce the AD/DA converter distortion. High SR (96-192 kHz) audio boards do not mean "ultrasound enabled" or "can record up to half the sampling frequency".
2) On the software side
Audio software generally provides a plethora of attractive filters, down-up sampling, interpolation, file format conversion tools, etc... for which very little is guaranteed or documented at "microscopic" level (phase distortion, for example) and although to your ear and on your spectrogram the job sounds and looks good, your data may be irreversibly unusable for fine analysis, like vocalization pattern recognition etc... Lots of tricks on audio softwares are pure and hardcore signal processing but meant for audio, human hearing, that the manufacturer won't even want to disclose information about when you need it.
This is where, for example, on both hardware and software sides, well-known instrumentation brands find a niche on the acoustic market - and are not always that expensive, why softwares like Ishmael were created (free, if i remember), and why lots of bioacousticians work with their well-known, regularly calibrated DAT machines (even if they sound old fashioned) or rough ten year old A/D acquisition boards, and process everything under Matlab - expensive or Octave -free!. The learning (and the initial expense) is tougher but always worth it eventually.
Still, an excellent audio recording station like a Pro Tools system may be turned into a scientific instrument for some applications that find its specs sufficient and adapted to the task. But, although i wish it were - and I am thinking of getting one for my home-studio, it is not aimed for acoustics but ... audio recordings, our human ears. Eventually, audio systems are not designed to provide more precision or signal integrity than what human hearing needs, and not the precision and integrity that your analysis may find necessary.
Best,
______________________________________________________ Eric Delory Laboratori d'Aplicacions Bioacustiques D164, Escola Polit�cnica Superior d'Enginyeria de Vilanova i la Geltr� Universitat Polit�cnica de Catalunya Avda. V�ctor Balaguer s/n 08800 Vilanova i la Geltr� Barcelona, Espa�a. Tel. (34) 93 896 27 72 Fax.(34) 93 896 77 00 H/P.(34) 655 33 0196 [EMAIL PROTECTED]
