Vocode-esque is an 8 band vocoding synthesizer with a custom display. This project aims to demonstrate a technique of signal analysis, decomposition and re-synthesis using a mixture of analog and digital circuity techniques. Instead of using DSP (Digital Signal Processor) chips, we used basic electronic components to build the synthesizer.

Vocode-esque filters   Vocode-esque CPU   The Sharp bandbass filters and CPU.      
Vocode-esque Bands   Vocode-esque board   The board got larger after a while.      
    The type of synthesis here is vocoding: An input signal is mixed in through an array of eight sharp bandpass filters. The filters F3db's were spaced linearly across the audible spectrum. Each filter feeds an integrator. The integrated magnitudes of each filter band then feed an analog to digital converter. The digital values are latched into the CPU. We chose to use a 8051 CPU in standalone configuration. The internal flash of the CPU was programed to perform two functions: 1. To to update an LED display, witch graphed a representation of the magnitude of each of the eight frequency bands; 2. To control eight digital pots on the output stage. The output stage consists of eight bandpass filters who's F3db's match the input filters. White noise feeds these filters.

The output of the filters are summed into speaker. The digital controlled pots are controlled by the CPU and attenuate the filters. The desired effect is a reconstructed sound made up from the 8 bands. It is a metallic or robot sound.
Vocode-esque board layers   Vocode-esque programming   Extra layers are used to fit all the components. The 8051 CPU is programmed in Assembly Language.      
Vocode-esque displays     Laser cut clear acrylics are designed to accommodate the LED array in a circular form. The center of the cylinder is used as a bus for all the wiring.      
    A cylindrical LED array display is built to show the energy in each of the bands. It is cut out of clear acrylic, and sandblasted to get a glow effect. The cylinder structure that holds the LEDs is designed to be visible from different angles. The center of the cylinder is used as a bus for all the wiring that goes from LEDs to the LED driver.

This work was the final project for Paul Horowitz and Tom Hayes's Physics 123 Lab at Harvard. Vocode-esque was a great lesson in analog-to-digital and digital-to-analog conversion.

Vocoder Wiki

DSP wiki
The Art of Electronics
Daft Punk