Time Stretching with Web Audio
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?
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.