Time Stretching with Web Audio

PaulStretch is an algorithm for extreme time stretching of audio. Sébastien Piquemal has ported the algorithm to javascript and built an interesting application for creating drone-style soundscapes from music imported from SoundCloud. In the accompanying blog post Sébastien explains how he used web workers to offload some of the heavy lifting to a background process which is an interesting technique in itself.

Web Audio Editor

Jan Monschke has published the source code for his collaborative multi-track audio editor on github. The README has a link to a presentation Jan gave at JSConf earlier this year, and a link to a working demo of the application. All of this work came out of Jan’s excellent MSc thesis which I covered in WAW 15.

Using Fourier Transforms with the Web Audio API

In this sitepoint article Sébastien Molines discusses the createPeriodicWave feature of the Web Audio API which lets you specify the parameters of an oscillator by way of the Fourier coefficients which make up your desired waveform. The article looks at how you can analyse an existing sound, such as a horn or police siren, and then use that analysis to create a convincing synthesis. It’s a powerful technique, and if you’re interested in exploring it further Welsh’s Synthesizer Cookbook applies similar techniques to the programming of analog synthesisers.

How Speakers Make Sound

Speakers (also called loudspeakers) push and pull surrounding air molecules in waves that the human ear interprets as sound. You could even say that hearing is movement detection. So what makes a speaker travel back and forth at just the right rate and distance, and how does that make sound?

A fantastic animated article by Jacob O’Neal sent to me by Tom Winter.

Mechanical Signal Analysis

Thor Magnusson shared this fascinating article and video series on a 19th Century machine for performing Fourier Decomposition - breaking a signal down into its constituent sine waves - using cogs, gears and pulleys. I was reminded of this yesterday when Ben Griffiths showed me Lord Kelvin’s tide-predicting machine which he’d seen at the Science Museum here in London.