Real-time spectrographic analysis with Sound Blaster sound boards [abstract]

Gianni Pavan and Ethan Brodsky (1997). Real-time spectrographic analysis with Sound Blaster sound boards [abstract]. Bioacoustics, Volume 8 (3-4): 278 -279

Spectrographic display of animal sounds has been widely used since the first analogue analysis instruments were developed for military acoustic research. However, until recently, the high cost of the specialized hardware necessary for this type of analysis made it inaccessible to most researchers. The recent development of digital signal processing techniques and high-speed hardware at relatively low-cost has made the real-time visualization of acoustic signals an every-day invaluable tool for bioacoustic research and education. A new version of the DSPW software already described in previous reports has now been developed to use CreativeTM Sound Blaster and compatible boards. The software strictly requires 16-bit sound boards (Sound Blaster 16, Sound Blaster 32 and true compatibles, including those based on the Vibra 16 chipset); it is DOS based and uses a high DMA channel (4-7) to perform continuous gap-free transfer of samples Nom the board to the computer memory. Since several notebooks now incorporate Sound Blaster compatible sound devices, this software opens up new perspectives in field applications. The software is a powerful display and analysis tool. Depending on the CPU speed (a Pentium is recommended), overlap and zero-padding can be performed in real-time to get sm00th time-frequency plots up to 44.1 ks/sec. Both spectrograms and cepstrograms can be computed in real-time. Three basic real-time display modes are available: horizontal display with envelope (wrap around or scrolling display), four strips scrolling display and vertical scrolling display. Even if cheap sound boards seem to be adequate for music and games, some problems are still to be solved when analyzing sounds: signal to noise ratio, bit resolution, frequency response, anti-aliasing filters, available sampling frequencies (most boards allow sampling rates ranging from 5 ks/s to 44.1 ks/s) and sampling frequency accuracy change depending on the sound board model. Thus, great care must be taken when using digitizing devices which are not designed for great accuracy. Before starting to use a particular sound device, a series of tests must be made. For this purpose, a collection of freeware utilities have been developed by Philip van Baren to check the real performances of Sound Blaster boards. A freeware version of the real-time software will be soon available on the net.