August 26, 2008

Psychoacoustic masking and audio compression

Jay Rose of DV and PVC has a four-part series on psychoacoustics and compression now posted as Hearing What’s Not There, Living with (Data) Loss, Vacuum Packed, and QuickTime Quickies.

Jay summarized the series like this:
  • What’s going on inside your head when you hear things
  • How psychoacoustic compression algorithms work
  • How lossless compression shrinks an audio file without any changes… but only if you’ve got a powerful computer
  • A few non-intuitive tricks that can streamline how you and your clients exhange audio over QuickTime.
Not covered in the referenced article from Nature Neuroscience but also fascinating is the cocktail party effect, which Wikipedia describes as "the ability to focus one's listening attention on a single talker among a mixture of conversations and background noises, ignoring other conversations" (like a complicated band-pass filter).

Note: SoundHack "is a soundfile processing program for the Macintosh. It performs many utility and esoteric sound processing functions available nowhere else. These functions make SoundHack invaluable to computer musicians, sound effects designers, multimedia artists, webmasters and anyone else who enjoys working with sound." At one point, SoundHack was the choice for resampling for many multimedia journeymen and audio geeks, and has branched into plug-ins for Windows and Mac.

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