Posts tagged "audio analysis"

Audio Analysis, Part 1: Digital Audio

Mon 16 November 2015

Spectogram of some recorded music

Today I'm going to try and explain how digital audio works. Most people have a vague idea about how sound works. "Sound is a wave!", they might say. "Sound bounces off things!", adds another. "Sound increases as you get closer to the stacks!", relates one subject matter expert. "What?", asks someone else? "I SAID SOUND INCREASES AS YOU GET CLOSER TO THE STACKS!" "Sorry I couldn't hear you over my crippling tinnitus! Dear Jesus if only I had known more about sound!"

This will be a really simple primer about digital sound waves and how they contain musical notes. To follow along at home, you'll need the excellent free audio editor Audacity. Download it if you don't have it already, then open it up to an empty window.

Right, so what does a single note "look" like? Let's start with a sine wave. Sine waves have an easily recognisable and pure-sounding tone. In our Audacity window, we'll click Generate -> Tone.

Audacity tone generator window

Oh look, they've helpfully picked a Sine wave as the default, with a frequency of 440 Hz and an amplitude of 0.8! (I changed the duration to only 5 seconds, as the default of 30 is a bit too long.) Let's hit OK.

Article continues here! KEEP READING, YOU