Real-time signal processing with PCs, without the need for dedicated DSP processors, has been made possible by the increase in C. PU performances. Increasing the CPU speed makes it possible (1) to increase the sampling rate, i.e. increasing the frequency range of the signals to be acquired, analyzed and displayed, (2) to perform complex analyses or (3) to process more than one channel at a time. Based on the low-cost Digital Signal Processing Workstation already described in previous reports, an updated version has been developed to allow real-time, dual-channel, spectrographic analysis and display of signals up to 48,000 samples/sec. The DSPW can now be used to acquire and analyze analog or digital stereo signals, depending on the installed I/0 ISA board (boards made by Audiologic-ltaly). An lntel Pentium P75 is required to perform dual channel analysis up to 48,000 s/s (22.5 kHz freq. range) while an Intel 486/66DX2 allows two channel processing up to 32,000 s/s (14 kHz freq. range); highly optimized DSP routines make it possible to get high resolution colour spectrograms that are perfectly synchronous with the sound. Dual channel analysis allows several new applications, including studying sound propagation and degradation with transducers at two different locations or analyzing stereo recordings of duetting birds. Further improvements will include some processing among channels and different analysis parameters for each channel. The workstation we have developed can provide real-time capabilities in the audio range with high resolution, quality and speed at a cost lower than that of dedicated workstations based on DSP processors. A great challenge for the coming years will be the development of portable instruments well suited to field research, in the audible range as well as in the ultrasonic one. The actual portable version of the DSPW relies on a Compaq Portable 486. Faster and lighter notebooks are now available for field use, but unfortunately PCMCIA acquisition cards to satisfy all the peculiar requirements of bioacoustic research are not yet available.
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