On-line Computer Control of a Formant Synthesizer
Cecil H. Coker, P. Cummiskey · The Journal of the Acoustical Society of America · 1965
A solid-state formant synthesizer has been constructed and interfaced to a digital computer. The computer, a DDP-24, has a 12K memory, and a 5-μsec cycle time. The computer-synthesizer combination permits on-line, real-time synthesis of speech under program control. The synthesizer has a number of useful features: optional serial or parallel operation; high-accuracy, wide-range control of three formant frequencies (±0.50% over a 20:1 range for F1); individual control of three formant bandwidths; unusual fidelity in spectral representation; and exceptionally low noise level. Amplitude controls are accomplished by linear multipliers with 60-dB range, hence frequency responses may be run with sine waves. Programming of the system is especially simple. Controls are normalized so that formant frequencies, bandwidths, and amplitudes at resonance are specified independently and without interaction. A data scan is accomplished under program control with only three instructions additional to those for computation. Alternatively, most of the data outputting can be done through a simultaneous memory access channel, with automatic program interruption for periodic servicing of the channel. Synthetic speech produced by the computer-controlled synthesizer is demonstrated.