There's actually a whole bunch of auditory illusions, even if you don't count audiovisual illusions like the McGurk Effect (splice someone saying "ga" together with video of that person saying "ba" and you perceive them as saying "da"; easily findable on Youtube).
One of the better known auditory illusions is the phenomenon of phantom or virtual pitch. Simply put, your normal perception of pitch is determined by the fundamental frequency (i.e. the lowest resonating frequency) of a given noise. However, if you build a sound entirely out of resonating frequencies that are all integer multiples of some other, lower frequency that is not present, people will hear the sound as having the pitch of that other, lower frequency.
Despite the fact, crucially, that there is simply no acoustic energy whatsoever in the signal at that frequency. None. At all. This utter lack of information doesn't keep your brain from perceiving the sound as if that phantom frequency was its fundamental.
Similarly, people tend to perceive very high frequency noises as coming from directly above their heads, regardless of the physical location of the actual source. This is the result of the specifics of the algorithms that your brain uses to localize sounds.
So there are definitely auditory illusions, even if they're a tad more subtle and tricky than visual illusions.
One of the better known auditory illusions is the phenomenon of phantom or virtual pitch. Simply put, your normal perception of pitch is determined by the fundamental frequency (i.e. the lowest resonating frequency) of a given noise. However, if you build a sound entirely out of resonating frequencies that are all integer multiples of some other, lower frequency that is not present, people will hear the sound as having the pitch of that other, lower frequency.
The inverse of which -- a dominant fundamental tends to mask out higher harmonics -- forms the basis of MP3 compression.
After listening to the Shepard's Scale a few times, I finally figured out how to defeat it: try to follow the highest note to its conclusion, and the 'reset' point will become more audible.
Classic punk band The Buzzcocks used the infinite scale, another term I've heard for the same phenomenon, at the end of their pretty sweet album Love Bites (I think, unless it was the end of Another Music In A Different Kitchen, their prior album) sometime around 1978.
Am I correct that the illusion seems to use the harmonics of the octaves to do some of its work?
It feels like the highest tone goes up a little higher than it really does, maybe a few notes higher. But perhaps that is because the highest tone really is still present as an overtone of the two lower notes.
So what we are really hearing is that what notes we hear as the fundamental on depends on the prior auditory context.
Also it is strangely hard to recognize when the high note becomes inaudible. For some reason that does not feel like a huge step down, maybe simply because the tones are crossfaded or something.
If you can find a recording of James Tenney's For Anne (Rising) he uses the same effect but with the tones separated in an 8:5 ratio, rather than a 2:1 (octave) which makes the different constituent frequencies more distinct. The piece lasts twelve minutes and it's an amazing experience to just play around in the sound.
MK, there are no harmonics in the tones since the effect is created using pure sine waves. Also, there's no crossfading; it's the frequency response of the human ear. The perception of eternal rising comes from the fact that your ear wants to hear the different tones as overtones of a fundamental since they're in a perfect 2:1 ratio. As a tone fades out of the audible range, your brain naturally picks out a lower one because it's so used to putting different frequencies together and hearing them as one when they correspond to neat, simple frequency ratios.
If you've listed to music in stereo, you've experianced auditory illusions.
There's actually a whole bunch of auditory illusions, even if you don't count audiovisual illusions like the McGurk Effect (splice someone saying "ga" together with video of that person saying "ba" and you perceive them as saying "da"; easily findable on Youtube).
One of the better known auditory illusions is the phenomenon of phantom or virtual pitch. Simply put, your normal perception of pitch is determined by the fundamental frequency (i.e. the lowest resonating frequency) of a given noise. However, if you build a sound entirely out of resonating frequencies that are all integer multiples of some other, lower frequency that is not present, people will hear the sound as having the pitch of that other, lower frequency.
Despite the fact, crucially, that there is simply no acoustic energy whatsoever in the signal at that frequency. None. At all. This utter lack of information doesn't keep your brain from perceiving the sound as if that phantom frequency was its fundamental.
Similarly, people tend to perceive very high frequency noises as coming from directly above their heads, regardless of the physical location of the actual source. This is the result of the specifics of the algorithms that your brain uses to localize sounds.
So there are definitely auditory illusions, even if they're a tad more subtle and tricky than visual illusions.
One of the better known auditory illusions is the phenomenon of phantom or virtual pitch. Simply put, your normal perception of pitch is determined by the fundamental frequency (i.e. the lowest resonating frequency) of a given noise. However, if you build a sound entirely out of resonating frequencies that are all integer multiples of some other, lower frequency that is not present, people will hear the sound as having the pitch of that other, lower frequency.
The inverse of which -- a dominant fundamental tends to mask out higher harmonics -- forms the basis of MP3 compression.
After listening to the Shepard's Scale a few times, I finally figured out how to defeat it: try to follow the highest note to its conclusion, and the 'reset' point will become more audible.
Classic punk band The Buzzcocks used the infinite scale, another term I've heard for the same phenomenon, at the end of their pretty sweet album Love Bites (I think, unless it was the end of Another Music In A Different Kitchen, their prior album) sometime around 1978.
King Crimson has also used this musically.
Am I correct that the illusion seems to use the harmonics of the octaves to do some of its work?
It feels like the highest tone goes up a little higher than it really does, maybe a few notes higher. But perhaps that is because the highest tone really is still present as an overtone of the two lower notes.
So what we are really hearing is that what notes we hear as the fundamental on depends on the prior auditory context.
Also it is strangely hard to recognize when the high note becomes inaudible. For some reason that does not feel like a huge step down, maybe simply because the tones are crossfaded or something.
If you can find a recording of James Tenney's For Anne (Rising) he uses the same effect but with the tones separated in an 8:5 ratio, rather than a 2:1 (octave) which makes the different constituent frequencies more distinct. The piece lasts twelve minutes and it's an amazing experience to just play around in the sound.
MK, there are no harmonics in the tones since the effect is created using pure sine waves. Also, there's no crossfading; it's the frequency response of the human ear. The perception of eternal rising comes from the fact that your ear wants to hear the different tones as overtones of a fundamental since they're in a perfect 2:1 ratio. As a tone fades out of the audible range, your brain naturally picks out a lower one because it's so used to putting different frequencies together and hearing them as one when they correspond to neat, simple frequency ratios.