5 ms·

Illusions of Sound Perception

76 points by DavidSJ 7y ago

dr_dshiv 7y ago
The Shepard tone illusion, of an ever rising pitch, is used in the movie Dunkirk https://www.businessinsider.com/dunkirk-music-christopher-nolan-hans-zimmer-2017-7 https://www.businessinsider.com/dunkirk-music-christopher-no...
- rrss 7y ago
  And the dark knight films. Apparently Nolan is fond of it.
  - dawnerd 7y ago
    And rightly so. It's incredibly effective at building suspense. Hans Zimmer's incredible scoring also helps.
CatrionaJasica 7y ago
The tiny hair cells in our inner ear send electrical signals to the auditory nerve which is connected to the auditory centre of the brain where the electrical impulses are perceived by the brain as sound. The brain translates the impulses into sounds that we know and understand
Stenzel 7y ago
There is no illusion of pitch, and it is a common misconception that the fundamental frequency must be present in a tone. Pitch is the perceived periodicity of a tone, which is roughly the greatest common divisor of the harmonics. If perceived pitch without fundamental is considered an auditory illusion with, common pitch detection techniques should fail if the fundamental is not present, but they work quite well in the absence of the fundamental. So either there is no illusion of pitch or algorithms have illusions too.
- DoctorOetker 7y ago
  the answer is: algorithms have illusions too. consider 2 ideal harmonic notes with a frequency ratio of 3:2, say 3kHz and 2kHz ... The brain / algorithm must doubt between interpreting the collection of frequency peaks at m * 3kHz, and n * 2kHz as either (occasionally overlapping) harmonics of 2 notes at 2kHz and 3kHz, OR it could interpret this as harmonics of a single note at 1kHz (as you say the GCD of the frequencies). There is inherent ambiguity between interpreting as 2 notes of each a timbre, vs interpreting as 1 note with another timbre... One could physically construct 3 bowed strings with modekilling on the 1kHz string, such that these could make perceptually identical sounds whether the 2kHz and 3kHz strings are played simultaneously vs the 1kHz string. at that point from the sound alone one can not discern in an ABX test which is the case, neither a human brain nor any algorithm. The doubt forces to guess (deterministically or not). The sound is a projection of properties occuring in reality, and loses information.
  - Stenzel 7y ago
    True, but ambiguity does not imply that one possible interpretation must necessarily be an illusion.
    - AstralStorm 7y ago
      Tones and harmonics get clustered into pitches, e.g. mistuned harmonics as seen in bass guitar or piano still get decoded into pitches via some sort of best match if the mistuning does not exceed certain percentage. And it works even if some harmonics disappear and reappear. The pitch is higher level than purely perceptual.
      - DoctorOetker 7y ago
        this is correct, and the reason we are tolerant is because of dispersion: even though the different harmonics are present on the same string of the same length, the resonant frequencies don't need to be integer multiples of the fundamantal since waves of different frequency have different propagation speeds on the string. in the case of bowed strings mode-locking ensures the phases of all the harmmonics are reset each cycle (the bow sticks and slips), so that bowed instruments can be played harmonically to parts per billion. since a lot of sounds are plucking we must be tolerant for frequency dependent propagations speeds in regular strings / media
tony 7y ago
For more: https://en.wikipedia.org/wiki/Auditory_scene_analysis https://en.wikipedia.org/wiki/Auditory_scene_analysis This book Auditory Scene Analysis: The Perceptual Organization of Sound by Albert S. Bregman has more. More foundational info on how we "fill in" information we see / hear https://en.wikipedia.org/wiki/Gestalt_psychology#Properties https://en.wikipedia.org/wiki/Gestalt_psychology#Properties
sp332 7y ago
Here is a video I enjoyed that explains the basics of how our sense of sound works. It makes it easier to understand why some of the illusions happen. https://vimeo.com/147902575 https://vimeo.com/147902575
- holy_city 7y ago
  Typo in the video (I think, not an anatomist), it's "basilar" membrane, not "vasilar." Awesome video though, I wish my speech processing professor had used that instead of teaching hearing like a filterbank, even if that is how we needed to understand it. Another weird thing about hearing: the hairs that vibrate aren't just tuned to particular frequencies, they actually vibrate over a range, and the response isn't symmetric (although iirc, part of that is from the fact the hairs are mechanically coupled). That's why low frequency noise masks high frequency noise more than vice versa, which is exploited in lossy codecs (if there's low frequency energy, you don't need high frequency energy that it masks).
  - sp332 7y ago
    That correction is in the video description, so yeah.
carapace 7y ago
See also "sine-wave speech". http://www.scholarpedia.org/article/Sine-wave_speech http://www.scholarpedia.org/article/Sine-wave_speech Oooo! Don't miss the acoustic chimera on that page...
anotheryou 7y ago
That was just one :/ I give you another one related one for rhythm: https://youtu.be/oQf_tS5WAP4 https://youtu.be/oQf_tS5WAP4

76 points by DavidSJ 7y ago

The Shepard tone illusion, of an ever rising pitch, is used in the movie Dunkirk https://www.businessinsider.com/dunkirk-music-christopher-nolan-hans-zimmer-2017-7 https://www.businessinsider.com/dunkirk-music-christopher-no...

rrss 7y ago
And the dark knight films. Apparently Nolan is fond of it.
- dawnerd 7y ago
  And rightly so. It's incredibly effective at building suspense. Hans Zimmer's incredible scoring also helps.

CatrionaJasica 7y ago

The tiny hair cells in our inner ear send electrical signals to the auditory nerve which is connected to the auditory centre of the brain where the electrical impulses are perceived by the brain as sound. The brain translates the impulses into sounds that we know and understand

Stenzel 7y ago

There is no illusion of pitch, and it is a common misconception that the fundamental frequency must be present in a tone. Pitch is the perceived periodicity of a tone, which is roughly the greatest common divisor of the harmonics. If perceived pitch without fundamental is considered an auditory illusion with, common pitch detection techniques should fail if the fundamental is not present, but they work quite well in the absence of the fundamental. So either there is no illusion of pitch or algorithms have illusions too.

DoctorOetker 7y ago
the answer is: algorithms have illusions too. consider 2 ideal harmonic notes with a frequency ratio of 3:2, say 3kHz and 2kHz ... The brain / algorithm must doubt between interpreting the collection of frequency peaks at m * 3kHz, and n * 2kHz as either (occasionally overlapping) harmonics of 2 notes at 2kHz and 3kHz, OR it could interpret this as harmonics of a single note at 1kHz (as you say the GCD of the frequencies). There is inherent ambiguity between interpreting as 2 notes of each a timbre, vs interpreting as 1 note with another timbre... One could physically construct 3 bowed strings with modekilling on the 1kHz string, such that these could make perceptually identical sounds whether the 2kHz and 3kHz strings are played simultaneously vs the 1kHz string. at that point from the sound alone one can not discern in an ABX test which is the case, neither a human brain nor any algorithm. The doubt forces to guess (deterministically or not). The sound is a projection of properties occuring in reality, and loses information.
- Stenzel 7y ago
  True, but ambiguity does not imply that one possible interpretation must necessarily be an illusion.
  - AstralStorm 7y ago
    Tones and harmonics get clustered into pitches, e.g. mistuned harmonics as seen in bass guitar or piano still get decoded into pitches via some sort of best match if the mistuning does not exceed certain percentage. And it works even if some harmonics disappear and reappear. The pitch is higher level than purely perceptual.
    - DoctorOetker 7y ago
      this is correct, and the reason we are tolerant is because of dispersion: even though the different harmonics are present on the same string of the same length, the resonant frequencies don't need to be integer multiples of the fundamantal since waves of different frequency have different propagation speeds on the string. in the case of bowed strings mode-locking ensures the phases of all the harmmonics are reset each cycle (the bow sticks and slips), so that bowed instruments can be played harmonically to parts per billion. since a lot of sounds are plucking we must be tolerant for frequency dependent propagations speeds in regular strings / media

tony 7y ago

For more: https://en.wikipedia.org/wiki/Auditory_scene_analysis https://en.wikipedia.org/wiki/Auditory_scene_analysis This book Auditory Scene Analysis: The Perceptual Organization of Sound by Albert S. Bregman has more. More foundational info on how we "fill in" information we see / hear https://en.wikipedia.org/wiki/Gestalt_psychology#Properties https://en.wikipedia.org/wiki/Gestalt_psychology#Properties

sp332 7y ago

Here is a video I enjoyed that explains the basics of how our sense of sound works. It makes it easier to understand why some of the illusions happen. https://vimeo.com/147902575 https://vimeo.com/147902575

holy_city 7y ago
Typo in the video (I think, not an anatomist), it's "basilar" membrane, not "vasilar." Awesome video though, I wish my speech processing professor had used that instead of teaching hearing like a filterbank, even if that is how we needed to understand it. Another weird thing about hearing: the hairs that vibrate aren't just tuned to particular frequencies, they actually vibrate over a range, and the response isn't symmetric (although iirc, part of that is from the fact the hairs are mechanically coupled). That's why low frequency noise masks high frequency noise more than vice versa, which is exploited in lossy codecs (if there's low frequency energy, you don't need high frequency energy that it masks).
- sp332 7y ago
  That correction is in the video description, so yeah.

carapace 7y ago

See also "sine-wave speech". http://www.scholarpedia.org/article/Sine-wave_speech http://www.scholarpedia.org/article/Sine-wave_speech Oooo! Don't miss the acoustic chimera on that page...

anotheryou 7y ago

That was just one :/ I give you another one related one for rhythm: https://youtu.be/oQf_tS5WAP4 https://youtu.be/oQf_tS5WAP4