VFX Article, Chapter 10

10. Where to go from here

The VFX processor was intended to demonstrate in an enjoyable way the capabilities of Digital Signal Processing (DSP). The four applications programmed into the VFX board are just four out of many possible applications. The VFX processor hardware is capable of being reprogrammed to perform other functions as well. Some of the possibilities are speech recognition, active noise cancellation, voice compression/recording and a spectrum shifting hearing aid. For example, the VFX processor could easily recognize the numbers form 0 to 9 and display them on the LED indicator. This requires that the speech be converted into the frequency domain and the spectral peaks of the sound be compared with prestored templates. The closest matching sound is selected and displayed on the LED. The processor then generates the DTMF signal for that number to make a voice activated telephone dialer. A voice compressor/recorder converts an audio input into the frequency domain, picks out the most prominent spectral energies and stores them in data memory as frequency and amplitude. This technique can reduce the data required as compared to straight digitization and storage from 6.5 k words per second to 650 to 300 words per second. The VFX board with 8 k words can record approximately 12 to 25 seconds compressed speech. Active noise cancellation is being developed for applications ranging from automobile mufflers and sound systems to fighter aircraft intercom system headphones. We will be working on these applications and will let you know when they are available. Let us know if you have any other applications you would like programmed into the VFX processor. If you are interested in programming your own applications, look into the EZ-LAB system sold by Analog Devices referred to in Appendix B. It is an affordable way to implement small to medium sized algorithms.

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