Audio "Optical" Illusions
May 04, 2006 by Vurdlak
This time "Mighty Optical Illusions" brings you another type of illusion. Audio illusions, also known as Audio Paradoxes are sometimes to be found in nature. The best known audio paradox is known as Shepard's paradox. It is the audio equivalent of the endless staircase illusion made famous by M. C. Escher. In this audio paradox a series of tones can be made to sound as if they are ascending or descending in pitch forever. You can download these three mp3's to see what I'm talking about. Huge thanks goes to noah.org for providing this illusion.
The following graph of Shepard's paradox shows frequency versus time. You can plainly see that the single pitch section appears to be increasing. Note that if the same graph is looped you can see that the finishing pitch is the same as the starting pitch.
It may be obvious to the eye, but the ear cannot perceive where the sample starts and finishes. If you listen to this sample the tones will appear to increase in pitch even if the sample loops back to the beginning and starts over. Here are the Audio Samples (pay attention that "repeat" button is turned on!):
Shepard's ascending tones (MP3) - This is a recording of Shepard's paradox synthesized by Jean-Claude Risset. Pairs of chords sound as if they are advancing up the scale, but in fact the starting pair of chords is the same as the finishing pair. If you loop this sample seamlessly then it should be impossible to tell where the sample begins and ends.
Falling bells (MP3) - This is a recording of a paradox where bells sound as if they are falling through space. As they fall their pitch seems to be getting lower, but in fact the pitch gets higher. If you loop this sample you will clearly see the pitch jump back down when the sample repeats. This reveals that the start pitch is obviously much lower than the finishing pitch.
Quickening Beat (MP3) - This recording is subtle. A drum beat sounds as if it is quickening in tempo, but the starting tempo is the same as this finishing tempo.
The following graph of Shepard's paradox shows frequency versus time. You can plainly see that the single pitch section appears to be increasing. Note that if the same graph is looped you can see that the finishing pitch is the same as the starting pitch.
It may be obvious to the eye, but the ear cannot perceive where the sample starts and finishes. If you listen to this sample the tones will appear to increase in pitch even if the sample loops back to the beginning and starts over. Here are the Audio Samples (pay attention that "repeat" button is turned on!):
Shepard's ascending tones (MP3) - This is a recording of Shepard's paradox synthesized by Jean-Claude Risset. Pairs of chords sound as if they are advancing up the scale, but in fact the starting pair of chords is the same as the finishing pair. If you loop this sample seamlessly then it should be impossible to tell where the sample begins and ends.
Falling bells (MP3) - This is a recording of a paradox where bells sound as if they are falling through space. As they fall their pitch seems to be getting lower, but in fact the pitch gets higher. If you loop this sample you will clearly see the pitch jump back down when the sample repeats. This reveals that the start pitch is obviously much lower than the finishing pitch.
Quickening Beat (MP3) - This recording is subtle. A drum beat sounds as if it is quickening in tempo, but the starting tempo is the same as this finishing tempo.
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That is very interesting. It hardly seems possible... but then I guess that most of the stuff on this blog hardly seems possible ;)
I only have a few flukes with the audios. i did put the first one on loop and could tell without looking at my player when it stopped and began. The falling bells is easy enough to hear, but the drum beat actually had me stumped! i tried conducting it, but just couldn't manage to stay at one tempo. overall, i do like these, though. :)
I only have a few flukes with the audios. i did put the first one on loop and could tell without looking at my player when it stopped and began. The falling bells is easy enough to hear, but the drum beat actually had me stumped! i tried conducting it, but just couldn't manage to stay at one tempo. overall, i do like these, though. :)
The third just sounds like reverb being adjusted
are these binded my any ownership rights? I would love to use them in my music. They all rock, I put them through cubase and looped em. http://www.myspace.com/wakeuprobot
hey i cant get mp3s, could you zip them?
Very cool!
The third one is especially cool.Can you explain how you did this?
i figured out the first two. in both clips, there is not one pitch playing at a time, but two, and they are octaves apart but the same note. as the scale progresses, the top note fades away and another, lower octave fades in on the bottom so that it is the same chord as it was in the beginning.
I could tell when the first started and stopped, I could tell that the second's pitch got higher, and that the third's tempo remained the same.
:/
No you didn't, Chantelle
Instead of “Audio "Optical" Illusions”, you should simply call that "Auditive Illusions". A motorcycle is not called a "motorized bicycle without pedal".
It seemed weird, but the first one is difficult to work out, but if listened close enough, and keeping the correct pitches in mind, it can be heard, although i think a person with perfect pitch might find this easier. On the second one it is clear to hear it gets higher in pitch, fairly simple to hear. The third one was odd though, although it does stay the same tempo, you just have o count the same beats, and then you can hear it all fit in.
There's a VST and Audio Unit plugin that generates this illusion:
http://mda.smartelectronix.com/effects.htm
Look for the Shepard plugin.
These illusions were cool... the first time you hear them =\
Shepard's illusion can be heard at the start of the Queen album 'A Day At The Races'
Agh, my heartbeat quickened on the last one.
i love the second one... it sounds cool...
none of the other ones worked.. ( i'm too old for the mosquito one apparently.. and i don't have headphones for the matchbox one ( i have speakers.. but only ONE works.... go figure) This one however.. tripped me out...
This "illusion" is also apparent in "Closer" by NIN during the chorus (where Trent sings "I want to **** you like an animal"), although the pattern doesn't progress through a complete scale.
qfkb nhlft abxpersdo wougnzxq vtpqzsflu yrcbgj vsqk
I am having a little trobule downloading the mp3s it will keep loading and never actually load. could you make them into a windows media player file or a real player or quicktime? that might make t easier.... love the illusions I can see, or hear!
It IS in Quicktime. Don't download the file. When you click on that link wait a bit and it plays.
the drum one sounds like the tempo is gradually doubled whilst some of the beats fade out so that you end up with the same drum beat.
Once upon a time I found an interactive flash of this paradox, something like a grey circle with yellow and red dots.
I found around the net but I lost the link =(
Anyway I think that J.S.Bach is cited in "Gedel Hescher and Bach" mainly for his "Canone Reale" (I don't know how is in english, sorry) that contain the same paradox.
Your site is fantastic and I will end loggin' in.
try listening to them all at the same time.
It will be the next hit
like those NOW pop music compilations.
These are well documented in Perry Cook's awesome book, Music, Cognition, and Computerized Sound. We experimental musicians have been playing with this stuff for more than 40 years.
-jim altieri
very cool stuff!
Brian May of Queen uses the Shepard's paradox to create an intro & outro guitar piece on Queen's A Day at the Races album.. The guitar 'symphony' appears to be continually going up and up..
Check it out if you want to hear a version of this that has been put together very seamlessly...
Interesting, but the illusion only works if you have the mp3 on repeat, and you focus on only one scale (the highest note going up or the lowest note going up). If you focus on a different note on the repeat, or if you alternate notes during, the illusion fails.