It doesn't have to be white - pink noise works the same just sounds more muffled/bassy. It's more that there is no distinct pattern in the time domain for the e

It doesn't have to be white - pink noise works the same just sounds more muffled/bassy. It's more that there is no distinct pattern in the time domain for the ear to pick out, which would add echoes or metallic ringing. The same as a boxy room or shower cubicle will ring/resonate at certain frequencies, but a bigger more complex shaped room will have an effectively random pattern of reflections for a given source and listener position.