And, if you know anything about the relation of frequencies to musical intervals, you know that the two “real” tones are a perfect fifth apart, while the “resultant” tone is an octave below the lower of the two real tones. For example, a 1,000 Hz tone coupled with a 1,500 Hz tone will create the illusion of a 500 Hz tone. When the frequency of the difference gets into the range of hearing, you hear the difference as its own tone. For example, if the one is 1,000 Hz and the other is 1,001 Hz, you will hear a once-per-second pulsation. Those beats are the difference in frequency between the two pitches. Similarly you can create an illusion of a sound particular pitch that doesn’t really exist (called a binaural pitch). If you want to know more about the science behind this, go to the web-page of Diana Deutsch, Professor of Psychology at San Diego, who developed many of these sound files.įor example, by playing two pure tones, one in each ear, at slightly different frequencies you will hear a beat where none really exists (called a binaural beat). The final seconds are great! Number 4 just features a box of matches.
Number 5 – ‘Virtual Barbershop’ features a session at the barber’s and is stupendous when listened to on headphones. These are examples of ‘dummy head’ recording. Hear (!) you perceive something in space, when it’s just in your head. This reveals that the start pitch is obviously much lower than the finishing pitch.’īut perhaps the most striking examples are only an illusion in the way perspective is a visual illusion – you can perceive something in 3-D that’s only really in 2-D. If you loop this sample you will clearly see the pitch jump back down when the sample repeats. As they fall their pitch seems to be getting lower, but in fact the pitch gets higher. Such as number 7 (‘Falling Bells’): ‘This is a recording of a paradox where bells sound as if they are falling through space. Some of them are illusions that are like visual illusions. This website contains 10 of the most fascinating auditory illusions. Or rather, it hurts, but there is no damage being done. And the ‘burning’ sensation you get from eating chili or curry is due to the fact that the pain receptors on your tongue (or your mucus membranes – ouch!) are activated by the capsaicins in the spice. ‘Phantom limb’ syndrome where amputees imagine they still have their limb (and, sadly, often feel pain in it) is an example of a touch illusion. Other kinds of sensory illusions are a bit trickier, however.
We all know about visual illusions, and the way that psychologists and neuroscientists use them to develop and test hypotheses about how the visual system works.
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