Signal Harmonization by Resampling to Design a Guitar Effect Pedal
Date
2016
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Videographer
Lighting Designer
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Swarthmore College. Dept. of Engineering
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Thesis (B.A.)
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en_US
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Full copyright to this work is retained by the student author. It may only be used for non-commercial, research, and educational purposes. All other uses are restricted.
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Abstract
A melodic audio signal harmonization algorithm was designed in MATLAB, implemented in C code, then run on a C2000 Piccolo F28069 Control Card and Experimenter's Kit from Texas Instruments. Using four output buffers, the algorithm generates a higher-octave harmony signal for an electric instrument signal. This is done by resampling, a process by which the signal, originally sampled at 44.1 kHz, is resampled at 22.05 kHz to produce output buffers containing every other data point of the input, causing a periodic signal to oscillate twice as quickly as the original signal. The raw guitar pickup output was amplified with an amplifier with a gain of 10 so that it could be read into the device. Crossfading between two output channels was implemented to eliminate an audible clicking artifacts that were a direct result of discontinuities present in the output signal. The output signal was sent directly from the device to a guitar amplifier to be played.