Jean Baptiste Joseph Fourier once stated that a composite wave can be represented as the sum of simple sine and cosine waves and this became the basis of the Fast Fourier Transform that is used to chop down waves into its sine and cosine components in order to analyze and identify frequency components of a signal.
A hundred years later – Andrei Mehiläinen demonstrated how to use a PIC32 proto board along with a 320×240 PX color LCD to build a simple audio spectrum analyzer. He used a 2048-point FFT (Fast Fourier Transform) algorithm to generate the frequency domain plot. The PIC’s ADC was configured to sample at 48kHz while two potentiometers are used to offset the input signal and to set the voltage reference. Firmware for the project was written using Microchip’s MPLAB C32 compiler. The audio spectrum analyzer can be connected to an unamplified signal source such as your computer’s sound card.