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Question about 1/f noise

For decades I’ve been reading about 1/f noise and have been curious what it sounds like. I’ve always been meaning to write a little program to generate some and then play it on a speaker, but I’ve never put the effort into figuring out exactly how to do it. But now with Google . . . there must be some 1/f noise out there already, right?

A search on “1/f noise” yielded this little snippet of 1/f noise simulated by Paul Bourke from a deterministic algorithm. It sounded pretty cool, like what I’d imagine computer music to sound like.

I did a little more searching on the web; it was easy to find algorithms and code for generating 1/f (“pink”) noise but surprisingly difficult to find actual sounds. I finally found this 15-second sinppet, which sounded like ocean waves, not like computer music at all! (You can compare to the sample of white noise, which indeed sounds like irritating static.)

I also found this online 1/f noise generator from a physics class at Berkeley. It works, also shows the amplitude series and spectrum. Also sounds like ocean waves. I’m disappointed–I liked the computer music. What’s the deal?

3 Comments

  1. Anonymous says:

    The "computer music" isn't 1/f noise as normally defined (or at least as normally understood). As you know, 1/f noise (a.k.a. "pink noise") has a power spectrum proportional to 1/f…that is, the amount of power in a particular frequency is inversely proportional to the frequency.

    Given _only_ the 1/f prescription, lots of wave patterns will fit the bill: for example, you could play a tone that steadily increases in frequency, while also getting quieter. Or you can play notes in some quasi-random way, choosing their frequencies appropriately, and end up with a power spectrum that goes like 1/f (that's what Bourke has done).
    But to most people, those aren't "1/f noise" because "noise" in this context is understood to have a stationary time-series. If someone played a tone that steadily increased in frequency while maintaining constant power, you wouldn't call it "white noise", for example.

  2. Jeff Zanooda says:

    The second sample sounds right. You can get similar result by tuning your FM radio to an unused frequency and setting the equalizer so that high frequencies are attenuated more.

    Paul Bourke's snippet sounded like a single wave that changes frequency at random. It sounds interesting, but it's is not pink noise. At any point in time its energy is concentrated in few spikes (harmonics), not spread like 1/f.

  3. Stuart Buck says:

    You've read the papers by Richard Voss on 1/f patterns in music, I take it? Fascinating how often 1/f noise crops up.