Hacker News Reader

It's a phenomenon that happens to all waves, whether they are acoustic or electromagnetic. In fact, it's how your clock radio tunes to various stations. This property is a mathematical property of all waves, hence even when your brain mixes an electrical representation of the sound going into your left and right ears, you still get the effect.

View on HN

For higher frequencies your auditory system doesn't retain the waveform information, so this doesn't happen.

I wonder if that's an evolutionary thing – somehow we evolved out the ability to retain phase difference information outside the frequencies where it's useful for stereo angular location?

The "~1000Hz" upper limit is pretty close to a 1/4 wavelength for a "phased array" of two ears ~100mm apart. That'd make it pretty ideal for angular discrimination based on phase difference.

You're pretty spot on here -- up to approximately 1500Hz, the auditory brain can make use of so-called inter-aural time differences which allow estimation of a given source's azimuth. After that, phase differences become ambiguous and the brain relies more heavily on inter-aural volume differences.

http://en.wikipedia.org/wiki/Interaural_time_difference

Reply on news.ycombinator.com