Image:DescenteInfinie.ogg

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DescenteInfinie.ogg (Ogg Vorbis sound file, length 1m6s, 42kbps)

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[edit] Summary

[edit] Comments

  • English : This is a Shepard-Risset glissando. I programmed this acoustic illusion in Java one year ago. Unfortunately, the source code is lost today because of a computer crash, but the equation is below.
  • Français : Ceci est un glissando de Shepard-Risset. J'ai programmé cette illusion acoustique en Java il y a un an. Le code source est malheureusement perdu (crash de mon ordinateur), mais l'équation est présentée ci-dessous.
  • Español : Este sonido es un Shepard-Risset glissando. Programe esta ilusion acustica hace un año en Java. Desafortunadamente, el codigo se perdio al estropearseme el ordenador pero la ecuacion esta abajo.

[edit] Equation

\,s T-periodic on \mathbb{R}

\forall t \in \left [0, T \right [

\,s(t) = a(t) \sin \left ( \omega(t) t \right ) + a(t + T) \sin \left (2 \omega(t) t \right )

with 
\begin{cases}
\begin{array}{lcl}
a(t) & = & A_0 \cfrac{1 + \cos \pi \frac{t}{T}}{4} \\
\omega(t) & = & 2 \pi F_0 \cfrac{1}{2^\frac{t}{T}} \\
F_0 & = & 220\,Hz \\
T & = & 20\,s \\
A_0 & = & 0.7
\end{array}
\end{cases}

The same signal is added on a minor chord, on several octaves, see details on my web site.

--Gloumouth1 01:39, 10 December 2005 (UTC)

[edit] Loop

If you want to have a loop, as T = 20 s, you can crop this sound exactly from 20 s to 40 s.

[edit] Another idea

If I (or you) have time, one day, another function which could be programmed and recorded...

\forall t \in \mathbb{R} \quad s (t) = \sum_{k=-\infty}^\infty a_k(t) \sin \left ( \omega_k(t) t \right )

with 
\begin{cases}
a_k(t)       =  A_0 e^{-\cfrac{ \left ( k-\frac{t}{T} \right ) ^2}{\sigma^2}} \\
\omega_k(t)  =  2 \pi F_0 2^{k - \frac{t}{T}} \\
A_0, F_0, T, \sigma \, constants
\end{cases}

--Gloumouth1 17:04, 5 March 2007 (UTC)

[edit] Licensing

This illustration was made by Gloumouth1.

Please credit this : Gloumouth1, http://gloumouth1.free.fr

An email to gloumouth1 at laposte.net would be appreciated too.

I, the copyright holder of this work, hereby publish it under the following licenses:
GNU head Permission is granted to copy, distribute and/or modify this document under the terms of the GNU Free Documentation license, Version 1.2 or any later version published by the Free Software Foundation; with no Invariant Sections, no Front-Cover Texts, and no Back-Cover Texts. A copy of the license is included in the section entitled "GNU Free Documentation license".

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This file is licensed under the Creative Commons Attribution ShareAlike 2.5 License. In short: you are free to share and make derivative works of the file under the conditions that you appropriately attribute it, and that you distribute it only under a license identical to this one. Official license
You may select the license of your choice.

josh

File history

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Date/TimeDimensionsUserComment
current21:40, 9 December 20051m6s (336 KB)Gloumouth1 (en:Shepard tone I programmed it in en:Java one year ago. --Gloumouth1 Category:Synthetic sound)