Now consider what happens when you play a note into the Instrument input while speaking into the Mic input. The Control Voltages used are the ones produced by the Mic filters and envelope followers. However, these filters are followed by Voltage Controlled Amplifiers (VCAs) so that the filter outputs may be amplified or attenuated by a Control Voltage increase or decrease.
These outputs go through individual envelope followers to provide eight Control Voltages (CVs) that track the energy in the part of the spectrum covered by the filter.įilters are also used to split the Instrument signal into eight different bands, which are tuned to the same frequencies as the Mic channel filters. Vowel sounds produce outputs from the various midrange filters. Similarly, speaking a plosive into the Microphone will give an output from the low frequency filters, while little (if any) signal will pass through the higher frequency filters. When you speak an “S” into the Microphone, the higher frequency filters fed by the Mic will produce an output but there will be no output from the lower frequency filters. One section of the vocoder uses band-pass filters to split the Microphone signal into eight frequency bands, each covering a specific part of the audio spectrum, somewhat like a graphic equalizer. Plosive sounds, such as “P”, “B”, on the other hand, contain lots of low frequency energy. An “S” sound, for example, contains lots of high frequencies. Talking into the Microphone impresses vocal effects on to whatever is plugged into the Instrument input via a fairly complex process, as described below.ĭifferent human speech sounds are associated with different parts of the frequency spectrum.
Usually, one input is for an Instrument such as keyboard or guitar, while the other is for a Microphone. A block diagram of the PAiA Vocoder is shown below - note that it has two inputs.
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