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Three tools for analysis-synthesis research on speech have been developed, employing an 18-channel vocoder as the basic speech processing device. One is a vocoder-playback (Voback) which produces speech sounds from hand-painted spectrograms. Frequency zones of the spectrogram corresponding to the pass bands of the channel filters are scanned by 18 multiplier phototubes to provide control voltages for the vocoder synthesizer. Two additional phototubes provide control of pitch and buzz/hiss switching. A second device (Intonator) permits arbitrary manipulation of the pitch of real speech as it passes through the vocoder. The speech is supplied to the vocoder from a loop of magnetic tape which runs in step with a variable-area pitch-control tape and a reference spectrogram. Phototubes supply pitch and buzz/hiss voltages to the vocoder synthesizer. A closely related device (Amplituder) permits instant-by-instant control of output level. A control voltage obtained from a phototube and variable-area tape is used to regulate a variable-gain output stage. Recordings from the three devices will be presented. (This work was supported in part by the Carnegie Corporation of New York, and in part by the Department of Defense in connection with Contract DA49-170-sc-1642.)
Borst et al. (Sat,) studied this question.