The White Noise of Smell

White noise is actually not perceptually neutral noise. It's mathematically random noise, with a flat power spectrum, meaning that for example the sound energy between 25-75 Hz is the same as that between 15000-15050 Hz. But because the human ear's perceptual loudness curve is not flat, the perceptual frequency distribution of white noise is not actually flat. To produce perceptually neutral noise, you need to apply the inverse of the human ear's perceptual loudness curve to white noise, which results in grey noise [wikipedia.org].

But beyond that, it seems they actually mean something different, more like "perceived as indistinct background noise". That's a wider range of things, and has to do with being able to resolve specific, distracting components, not necessarily with mathematical definitions of noise.

Source: http://rss.slashdot.org/~r/Slashdot/slashdotScience/~3/BwfjcQ5jbAQ/story01.htm

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