aphaser

Watch on youtube.com
doc

https://ffmpeg.org/ffmpeg-filters.html#aphaser

The description in the official documentation:

Add a phasing effect to the input audio.

A phaser filter creates series of peaks and troughs in the frequency spectrum. The position of the peaks and troughs are modulated so that they vary over time, creating a sweeping effect.

Each segment of the uploaded video was created with the following script:

#! /bin/sh
ffmpeg -hide_banner -y -filter_complex "
amovie=wolframtones_01.wav
,atrim=0:15,afade=t=out:st=14.5:d=0.5

,aphaser=
 in_gain=0.4
:out_gain=0.74
:delay=3.0
:decay=0.4
:speed=0.5
:type=t

,aformat=sample_fmts=u8|s16:channel_layouts=stereo
,asplit=3[out1][a1][a2];
[a1]showfreqs=s=$((1280/5*3))x720:fscale=log:cmode=separate[v1];
[a2]showwaves=s=$((1280/5*2))x720:mode=cline:split_channels=1[v2];
[v2][v1]hstack
,format=yuv420p
[out0]" -map '[out0]' -map '[out1]' out.mp4

The effect of this is so obvious that I won’t say anything.

see also

flanger