With the settings on page 18 and Spectravox’s output
connected to a monitoring system (or headphones), you
should hear a vocoded signal as you speak into your
microphone! If you don’t, make sure to adjust the GAIN
LEVEL control below the PROGRAM INPUT so that the
LED indicates a nice strong signal—bright red at the
loudest parts of your voice.
Spectravox’s sound is distinct, capturing rich analog
vocal tones with its 10 filter bands. Speak and sing into
Spectravox and listen to how it responds to the dierent shapes your mouth makes.
NOTE: Just like Homer Dudley in 1939 and Wendy Carlos in 1970 had to do, the only way to get speech with any
kind of intelligibility is to enunciate your words with the utmost precision and clarity!
With our current settings the carrier signal is just the pulse VCO with PULSE WIDTH set to around 10
o’clock and with the BANDS 9 & 10 switch set to HISS. This is ideal for a vocoded speech-like sound.
The VCO replicates the vibration of vocal cords and is the basis for voiced sounds. In English, all
vowels, all diphthongs, and some consonant sounds are voiced. Notice how when you say the word
“sent” your vocal cords vibrate only during the voiced parts of the word: during the ‘e’ and ‘n’ sounds.
For the ‘s’ at the beginning and the ‘t’ at the end, your vocal cords stop vibrating and instead you make
the sounds by pushing air through your teeth. These unvoiced sounds are best replicated by noise
instead of by an oscillator.
You can turn SPECTRAL SHIFT down from 12 o’clock just a little bit to simulate
a formant shift to a deeper voiced person, or increase it a little bit above 12
o’clock to simulate an upwards formant shift to a higher voiced person.
The operators of the original Voder back in 1939 had a switch called HISS/
BUZZ to switch the carrier signal between noise and a VCO for unvoiced or
voiced tones. Spectravox does this automatically with the BANDS 9 & 10 switch
set to HISS—replacing the carrier with noise in the highest two filters (9 & 10)
whenever an unvoiced tone is detected in the PROGRAM signal. Setting this
switch to BUZZ simply sends the same CARRIER signal in all of the other bands
to the top two bands as well. Play around with the BANDS 9 & 10 switch as you
speak dierent words into Spectravox and listen to the dierence when you
pronounce sibilant sounds like ‘s’ or plosives like ‘t’ and ‘d.’
NOTE: You can always introduce a little NOISE by fading some in with the CARRIER MIX control to add some
raspiness to your synthetic voice.
19
EXPLORING SPECTRAVOX (Continued)
GAIN LEVEL
SPECTRAL SHIFT
BANDS
9 & 10
HISS
BUZZ
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