Just-noticeable amplitude modulation of noise shrinks from 40% to 6% as bandwidth widens.

Evidence

At very narrow bandwidths, the just-noticeable degree of amplitude modulation is near 40%, i.e. quite large and not comparable to that produced by a sinusoidal tone. With increasing bandwidth, the just-noticeable degree of amplitude modulation decreases and reaches the value of about 6% at a bandwidth of 2 kHz (about one critical band). — Professor Dr.-Ing. Hugo Fastl, Professor Dr.-Ing. Eberhard, Psychoacoustics- Facts and Models, 1024