MadSci Network: Engineering

Re: How do i make a voice transformer? (change my voice )

Date: Wed Jan 17 16:22:08 2001
Posted By: William Beaty, Electrical Engineer / Physics explainer / K-6 science textbook content provider
Area of science: Engineering
ID: 977064477.Eg

Here's a magazine article. (I don't have this issue, so I can't verify if it's correct)

Radio Electronics (magazine) January 1993
"Build Your Own Digital Voice Changer"
Here is a schematic which uses a Holtek HT8950 voice-changer chip.
One very simple method of changing your voice is shown on this webpage below, but it can only make your voice LOWER in frequency:
If you want to do it yourself, one way to change your voice is to pass it through a "balanced modulator" circuit such as an ANALOG MULTIPLIER chip (for example the Motorla MC1494 chip.) You feed a sine wave into one input, feed the audio signal into the other input, and the output is a weirdly scrambled voice. (multiplying a voice spectrum by a sine wave actually gives you a "sum" spectrum where the voice frequency is higher, and a "difference" spectrum where the voice frequencies are both lower and also backwards!) Tune the sine wave frequency to change how the voice sounds.

A true "pitch bender" circuit uses two analog multipliers, two separate sinewave oscillators, and various filters and op-amps. Each sinewave signal is sent to one input of each multipler. The original audio is sent to the other input of the first multiplier, which creates "sum and difference" frequencies on its output. A low-pass filter then removes the "sum" frequencies. The result is sent to the second multipler, which creates DIFFERENT sum/difference frequences because its sinewave oscillator is not set the same as the first one. A low-pass filter then removes the "sum" frequencies, and the output result is normal audio. But if the frequencies of the two sinewave oscillators are not set exactly the same, then the audio output will be shifted in frequency. You can make guys sound like gals and vice versa.

Also see:


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