Have you ever wanted to build devices that react to audio, but have been unsure about or even intimidated by analyzing signals? Don’t worry! This guide is an overview of applying the Fourier transform, a fundamental tool for signal processing, to analyze signals like audio. I’ll show you how I built an audio spectrum analyzer, detected a sequence of tones, and even attempted to detect a cat purr–all with a simple microcontroller, microphone, and some knowledge of the Fourier transform.
Continue on to learn some background information about the Fourier transform.