1. Sounds like three notes on three different octaves. The low note is constant and actually restarts. The Middle note fades in and the high note fades out. Taken together it sounds like one sound that is just changing characteristics. Something we’re quite used to sounds doing coming from instruments. Wonder if you could make an orchestra reproduce this illusion…

  2. I’m not paying attention in class at the moment so I haven’t heard this particular one, but in ones like this I’ve seen before you have a recording of rising tones that you play out of phase with itself that fades in and out gently so you don’t notice the end of the loop. Then your brain gets confused and latches on to the lower octave, thinking it’s the higher octave.

    Also kinda fun: what’s the highest note you can think of?

    1. but it starts with apparently the same note as it ended, hence the illusion if continously rising series of notes.

  3. Led Zep used this type of auditory illusion in their song Kashmir. I can’t exactly remember why we perceive the effect the way we do but I think wraakh’s explanation is somewhere in the ballpark.

  4. Mad Kev has a point. The illusion is spoilt because the clip is so short and has to be restarted frequently. Can someone find a better implementation?

  5. It’s called the Shepard scale.

    Each sound consists of several tones, all rising in frequency, but as the highest tone go up it’s gradually faded out and replaced by a low tone that is faded in.

    In a way it’s like a spotlight on an escalator where each step is a tone, and where you only see a few steps in the spotlight. They all seem to be rising endlessly but the trickery where the highest step becomes the lowest is obscured.

  6. I have a sound like this on my keyboard. It contains enough harmonics so that you don’t notice the top ones drop out and the new low ones come in. Here is an example of a scale played three times:
    The illusion is enhanced by expectation; an organ at one octave sounds pretty much like the same sound one octave higher and by expecting it to be higher you don’t notice when the sound has actually dropped one octave.

  7. You hear the rising tones, but not the end or beginning of the tones, because there’s always at least one where your ear expects it. There’s a different way to do this with beat frequencies, but I don’t think this sound is that complex.


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