Basic:
brew install sox
play -n synth brown
https://www.cloudacm.com/?p=3145
play -n synth 60:00 whitenoise
play -n synth 60:00 pinknoise
play -n synth 60:00 brownnoise
The SoX examples given thus far generate a noise that is mono, meaning the left and right channels are identical. In this example, we’ll generate noise for each left and right channel and merge them together for a single stereo output.
play -n -n --combine merge synth '24:00:00' brownnoise
play -n -n --combine merge synth '24:00:00' brownnoise band -n 750 750 tremolo 50 1
https://askubuntu.com/questions/789465/generate-white-noise-to-calm-a-baby
After experimenting a bit with SoX, I came up with this great command which imitates the soft murmur of the sea with its soothing sound of waves that flow over a flat sandy beach on a sunny summer day...
This command first generates and mixes brown noise and pink noise, which I find to be the most comfortable and natural noise. Then it generates a sine wave of 0.3 Hz with an offset of 10% and uses this to modulate the amplitude of our mixed noises to produce the sound of ocean waves.
Change 0.3 to e.g. 0.1 for "slower" "waves"
play -n synth brownnoise synth pinknoise mix synth sine amod 0.3 10
Change 10 to e.g. for stronger or weaker background noise
play -n synth brownnoise synth pinknoise mix synth sine amod 0.3 20
Tweaked version
play -n synth brownnoise synth pinknoise mix synth 0 0 0 10 10 40 trapezium amod 0.1 30
Another pink noise "recipe"
play -t sl -r48000 -c2 -n synth -1 pinknoise .1 60