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Reputation: 4534

Add low frequency amplitude modulation to noise

I am trying to reproduce a SoX script using ChucK which creates brown noise with a slight oscillation (tremolo).

The SoX script is:

set -u
set -e

minutes=${1:-'59'}
repeats=$(( minutes - 1 ))
center=${2:-'1786'}

wave=${3:-'0.0333333'}

noise='brown'

len='01:00'

if [ $minutes -eq 1 ] ; then
     progress='--show-progress'
else
     progress='--no-show-progress'
fi

echo " ::  Please stand-by... sox will 'play' $noise noise for $minutes minute(s)."

play $progress  -c 2  --null  -t alsa  synth  $len  ${noise}noise  \
     band -n $center 499               \
     tremolo $wave    43   reverb 19   \
     bass -11              treble -1   \
     vol     14dB                      \
     repeat  $repeats

exit 0

The following ChucK script, modified from the wind2.ck example, creates brown noise of the desired frequency:

Noise n => BiQuad f => dac;
0.99 => f.prad;
0.0333333 => f.gain;
1    => f.eqzs;
0.00 => float t;
while(true)
    5::ms => now;

I am unable to reproduce the effect that the SoX tremolo option creates.

It seems like I should be able to add a Sine wave to the main chain and then oscillate that parameter. I am trying variations of FM.ck frequency modulation example without success:

SinOsc m => Noise n => BiQuad f => dac;
20 => m.freq;
200 => m.gain;
0.99 => f.prad;
0.0333333 => f.gain;
1    => f.eqzs;
0.00 => float t;
while(true)
    30 + ( Math.sin(t) + 1.0 ) * 10000.0 => m.sfreq;
    t + .004 => t;

    5::ms => now;

I expect to hear some fluctuation in the tone, but instead, no sound appears to be produced.

How can I add a low frequency amplitude modulation to the brown noise I've generated?

Upvotes: 1

Views: 111

Answers (0)

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