A PC-based digital speech spectrograph

The author describes how a TMS32010-based Tl-speech PC board from Texas Instruments was combined with an off-the-shelf, PC graphics board to produce a real-time speech spectrograph system. The Realtime Spectral Lab (RSL) is a relatively inexpensive, PC-based, commercial-quality system. It produces high-quality spectrograms of up to 2 s of speech within 5 s of speech input. Also discussed are the algorithms chosen and the software structures evolved to implement the system. The resulting instrument is flexible. Dual spectrograms can show either simultaneous wideband and narrowband analyses of the same utterance, or equal frequency-resolution versions with differing time resolution. In addition, users can compare a target spectrogram to changing, real-time input. They can also mark a wideband spectrogram with cursors and expand the selected time segment into another, fine time-resolution spectrogram. The discussion is a case study of nontrivial DSP (digital signal processing) systems design and implementation by hardware selection and DSP programming alone.<>