viernes, 2 de octubre de 2009

Audio illusions

Top 10 según alguien

Diana Deutsch's Audio Illusions

Shepard Illusion

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 upwards or downwards, 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. (Keep reading on wikipedia)

Tritone Paradox

The tritone paradox is an auditory illusion in which a sequentially played pair of Shepard tones [1] separated by an interval of a tritone, or half octave, is heard as ascending by some people and as descending by others.[2] Different populations tend to favor one of a limited set of different spots around the chromatic circle as central to the set of "higher" tones. The tritone paradox was first reported by psychology of music researcher Diana Deutsch in 1986(Keep reading on wikipedia)

Oir, entzun, hear.
Discovered by Diana Deutsch in 1973, the octave illusion is an auditory illusion produced by simultaneously playing two sequences of two notes that are spaced an octave apart, high to low, and low to high, in separate stereo channels over headphones. The tones are sine waves of constant amplitude, and switch between high and low four times a second, with no amplitude drops at the transitions. So the listener is presented with a single, continuous two-tone chord, with the ear of input of each component switching repeatedly. (Listen over headphones to the Stereo Sound Example linked below.) This pattern is almost never heard correctly, and instead gives rise to a number of illusions. Most people hear a single tone that switches between left and right ears while its pitch simultaneously switches back and forth between high and low. Most right-handers hear the high tone as on the right and the low tone as on the left. When the earphones are reversed most right-handers hear the same thing – the tone that had appeared in the right ear still appears in the right ear and the tone that had appeared in the left ear still appears in the left ear.
Other people experience entirely different illusions; for example they may hear a single high tone in the left ear alternating with a single low tone in the right ear, or obtain complex perceptions that involve three or four tones of different pitch. Righthanders and lefthanders vary statistically in how they perceive the octave illusion, with left-handers less likely to hear the high tone on the right, and more likely to obtain complex perceptions.

It is easy to produce variants of the scale illusion. One is the chromatic illusion, which was first published by Deutsch, Audio Magazine, 1987.
A chromatic scale is presented that ranges over two octaves. The scale is presented in both ascending and descending form, with the individual tone switching from ear to ear as in the original scale illusion. When the pattern is played in stereo, many people hear a higher line that moves down an octave and up again, together with a lower line that moves up an octave and down again, with the two meeting in the middle. Yet when each channel is played separately, it is heard correctly as a series of tones that jump around in pitch. The figure below shows the pattern producing the chromatic illusion and how it is perceived. When played through stereo headphones, righthanders again show a tendency to hear the higher tones on the right and the lower tones on the left, but lefthanders as a group are much more variable in terms of what they hear. For other variants of the scale illusion, see Butler, 1979.

Deutsch's scale illusion
Discovered by Diana Deutsch in 1973, Deutsch's scale illusion is an auditory illusion produced by simultaneous ascending and descending major scales beginning in separate stereo channels with each successive note being switched to the opposite channel. With the left channel: C'-D-A-F--A-D-C'; and the right: C-B-E-G-E-B-C; the ear hears both: C'-B-A-G--A-B-C'; and: C-D-E-F--E-D-C. The tones are equal-amplitude sine waves, and the sequence is played repeatedly without pause at a rate of four tones per second. (Listen to the Stereo Sound Example linked below.)
When listening to the illusion over headphones, most right-handers hear a melody corresponding to the higher tones as on the right and a melody corresponding to the lower tones as on the left. When the earphone positions are reversed, the higher tones continue to appear to be coming from the right and the lower tones from the left. Other people experience different illusions, such as the higher tones on the left and the lower tones on the right, or a pattern in which the sounds appear to be localized in different and changing ways. Right-handers and left-handers differ statistically in how the scale illusion is perceived As with all (most?) other sensory illusions, they are the result of the actions of the brain to "clean" the data it's fed in order to make sense of it. In this case, it perceives 2 logical signals each made of half of the notes, as opposed to a string of random occurrences for each note. Whenever there is a correlation, the brain tries to make a pattern out of it. The pattern may not be 100% accurate or what the original sender intended it to be, but it usually is accurate enough for a species to evolve training its natural neural net. Any crude signal processor can be fooled. Any complex signal processor may be too complex, big, expensive, slower than realtime etc. to be of any practical use. Practical, in our case, meaning balancing costs/efficiency to assure survival/evolution

Salvatore Sciarrino

Una anamorfosis o anamorfismo es una deformación reversible de una imagen producida mediante un procedimiento óptico (como por ejemplo utilizando un espejo curvo), o a través de un procedimiento matemático.

(Del gr. ἀναμόρφωσις, transformación).
1. f. Pintura o dibujo que ofrece a la vista una imagen deforme y confusa, o regular y acabada, según desde donde se la mire.

Bien ahora que sabemos esto oimos esto otro: Anamorfosi (sciarino)

Parece una versión de esta otra¿no?: Jeaux d'eau, de Maurice Ravel.

Si. Vale. Ahora el titulo: Anamorfosi... ¿Por qué?.... Abra una melodía escondida por ahí, pero ¿cúal?. Una vez que la oyes no hay pérdida. :)


(Para los que no la encuentran, click aqui).

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