• 21 Aug, 2019

• By, Wikipedia

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Wikipedia  This is a featured sound on the English language Wikipedia (Featured sounds) and is considered one of the finest sound files. See its nomination here. If you think this file should be featured on Wikimedia Commons as well, feel free to nominate it. If you have an image of similar quality that can be published under a suitable copyright license, be sure to upload it, tag it, and nominate it.

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

${\displaystyle \forall t\in \left[0,T\right]}$

${\displaystyle \,s(t)=a(t)\sin \left(\omega (t)t\right)+a(t+T)\sin \left(2\omega (t)t\right)}$

with ${\displaystyle {\begin{cases}{\begin{array}{lcl}a(t)&=&A_{0}{\cfrac {1+\cos \pi {\frac {t}{T}}}{4}}\\\omega (t)&=&2\pi F_{0}{\cfrac {1}{2^{\frac {t}{T}}}}\\F_{0}&=&220\,{\text{Hz}}\\T&=&20\,{\text{s}}\\A_{0}&=&0.7\end{array}}\end{cases}}}$

The same signal is added on a minor chord, on several octaves.

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

If you want to have a loop, as T = 20 s, you can crop this sound exactly from 18 s to 38 s.

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

${\displaystyle \forall t\in \mathbb {R} \quad s(t)=\sum _{k=-\infty }^{\infty }a_{k}(t)\sin \left(\omega _{k}(t)t\right)}$

with ${\displaystyle {\begin{cases}a_{k}(t)=A_{0}e^{-{\cfrac {\left(k-{\frac {t}{T}}\right)^{2}}{\sigma ^{2}}}}\\\omega _{k}(t)=2\pi F_{0}2^{k-{\frac {t}{T}}}\\A_{0},F_{0},T,\sigma \,{\text{constants}}\end{cases}}}$

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

en:File:DescenteInfinie.ogg