anoisesrc

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doc

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

#! /bin/sh
# Don't forget to specify amplitude because it will be
# annoying in your neighborhood. White noise is particularly
# noisy.
ffplay -f lavfi 'anoisesrc=a=0.1:c=white'

#! /bin/sh
# specifying a duration
ffplay -f lavfi 'anoisesrc=a=0.1:c=white:d=5'

#! /bin/sh
# visualize by ahistogram
ffplay -f lavfi '
anoisesrc=a=0.1:c=white,asplit[out1],ahistogram[out0]'

#! /bin/sh
ffplay -f lavfi '
anoisesrc=a=0.1:c=pink,asplit[out1],ahistogram[out0]'

#! /bin/sh
ffplay -f lavfi '
anoisesrc=a=0.1:c=brown,asplit[out1],ahistogram[out0]'

c=blue, and c=violet is not available in ffmpeg 3.3.2:

#! /bin/sh
"/c/Program Files/ffmpeg-4.1.1-win64-shared/bin/ffmpeg" -filter_complex '
anoisesrc=a=0.1:c=blue,asplit[out1],ahistogram[out0]
' -map '[out0]' -map '[out1]' -f matroska - | ffplay -

#! /bin/sh
"/c/Program Files/ffmpeg-4.1.1-win64-shared/bin/ffmpeg" -filter_complex '
anoisesrc=a=0.1:c=violet,asplit[out1],ahistogram[out0]
' -map '[out0]' -map '[out1]' -f matroska - | ffplay -

Trying all colors and its visualize:

#! /bin/sh
# c=blue, and c=violet are not available in ffmpeg 3.3.2.
ffmpeg="c:/Program Files/ffmpeg-4.2.1-win64-shared/bin/ffmpeg"
#
for f in 'aevalsrc=random(0):d=8' \
         'anoisesrc=c=white:d=8' \
         'anoisesrc=c=pink:d=8' \
         'anoisesrc=c=brown:d=8' \
         'anoisesrc=c=blue:d=8' \
         'anoisesrc=c=violet:d=8' ; do
("${ffmpeg}" -filter_complex "
${f}
, asplit=5[a0][a1][a2][a3][a4];
[a0]volume=0.1[out1];
[a1]ahistogram=s=512x286[v1];
[a2]abitscope=s=512x286[v2];
[a3]showcqt=s=512x286[v3];
[a4]showspectrum=s=512x286[v4];
[v1][v2]hstack[vt];
[v3][v4]hstack[vb];
[vt][vb]vstack,format=yuv420p
,drawtext=fontsize=40:fontcolor=white:x=50:y=300:
text=`echo ${f} | sed 's@:@\\\\\\\\:@g'`[out0]
" -map '[out0]' -map '[out1]' -f matroska - | \
    ffplay - -autoexit 2>/dev/null)
done

Adding noise to input audio

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Adding white noise to input audio:

#! /bin/sh
ffplay -f lavfi "
anoisesrc=c=white:d=30:a=0.01,asplit,join[s1];
amovie=some.wav[s2];
[s1][s2]amix"

#! /bin/sh
# visualizing
ffplay -f lavfi "
anoisesrc=c=white:d=30:a=0.01,asplit,join[s1];
amovie=some.wav[s2];
[s1][s2]amix
,asplit=3[out1][a1][a2];
[a1]showfreqs=s=$((16*60/4))x$((9*60)):cmode=separate:fscale=log[v1];
[a2]showcqt=s=$((16*60/4*3))x$((9*60))[v2];
[v2][v1]hstack[out0]"

Note

$((...)) is a buit-in of bash, not of ffmpeg. See About `shell’ script.

Adding white noise to the left channel and pink noise to the right channel:

#! /bin/sh
ffplay -f lavfi "
anoisesrc=c=white:d=30:a=0.2[n1];
anoisesrc=c=white:d=30:a=0.1[n2];
[n1][n2]join[s1];
amovie=some.wav[s2];
[s1][s2]amix"

#! /bin/sh
# visualizing
ffplay -f lavfi "
anoisesrc=c=white:d=30:a=0.2[n1];
anoisesrc=c=white:d=30:a=0.1[n2];
[n1][n2]join[s1];
amovie=some.wav[s2];
[s1][s2]amix
,asplit=3[out1][a1][a2];
[a1]showfreqs=s=$((16*60/4))x$((9*60)):cmode=separate:fscale=log[v1];
[a2]showcqt=s=$((16*60/4*3))x$((9*60))[v2];
[v2][v1]hstack[out0]"