I am studying computational mathematics and so we often deal with sound manipulation algorithms.

As this study has piqued my interest in the subject I was wondering how to go about learning some of the neatest engineered sounds that I hear.

My question is about the sound that occurs from seconds 0:14-0:24 in this song on youtube

. What is it called to have a sound fade away in this manner? How could I go about finding the mathematical underpinnings of how this is achieved (so that I can recreate this effect myself)?

Thank you for your help!

2 Answers 2


This is being achieved using an automated low-pass filter. a Low-pass filter is set up in the signal chain and the value of the cut-off frequency value is being modified by an underlying automation parameter across this time-range in the timeline. There are a number of layers of sound going on here as well - also sounds like there is a reverse reverb in play. This is where a reverb tail is edited out and played in reverse as the 'introduction' to the next segment of music.

  • There is also a beat-synched echo/delay in there which also has attenuation/decay on the feedback.
    – Mark
    Dec 18, 2016 at 9:34

i think he is just talking about the delay

Basically it samples the incoming signal and then feeds back the sampled signal back into the chain after a specific delay and a specific percentage of the initial volume.......Always lower than the initial volume as of course if it was louder it would keep getting louder theoretically forever wich isnt a good thing (or until something breaks or you hit your headroom and start making squarewaves instead....)

As far as the math.....The higher percentage you feed back the longer(more iterations) of the origional signal you will have....But make sure that the delay matches up with the timing of the song....For example if you are playing 4/4 and 1 bar is exactly 1 second then your initial delay can either be 1 second (so the first iteration will be on the first beat of the next bar) or half a second (first iteration on 3rd beat of 1st bar) or 1/4 (first iteration on second beat of the bar) or 1/8 (first iteration halfway between first and second) etc etc..... Gotta make the math work ...Delays work so much better when you do the math and match the bpm of the music ....

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