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Audio illusion
Listen to this video until the end, and when it stops, play it again to hear the difference. A Shepard tone, named after Roger Shepard, is a sound consisting of a superposition of sine waves separated by octaves. When played with the base pitch of the tone moving upward or downward, it is referred to as the Shepard scale. This creates the auditory illusion of a tone that continually ascends or descends in pitch, yet which ultimately seems to get no higher or lower.[1] It has been described as a "sonic barber's pole".
Posted 10 years ago by anri1 in category: science
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anri1 - 10 years ago [ Reply ]
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Just like there are optical illusions, there is also “audio illusion” or "accoustical illusion". This one is called Shepard Tone. When a number of octave notes are played at the same time, the average human ear will simply hear the one note, closest to the last pitched sound it heard, as opposed to differentiating and splitting that sound into its singular octave parts. The volume of the higher pitched tone slightly decreases and the lower pitched one increases over the scale, which is what makes the effect seem so seamless.

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causeby - 10 years ago [ Reply ]
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anri1 is right. If you skip from 3/4 of the way through back to 1/4 of the way through, the apparent pitch does go down. The effect works because the center of the loop is at the front an back of the video.

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anri1 - 10 years ago [ Reply ]
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Thank You causeby.

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spydyrman - 10 years ago [ Reply ]
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thanks for the explanation! Makes a lot more sense now.

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