In contrast to white noise, pink noise has more energy in the lower frequencies. Since pink noise has relatively more bass than white noise, it sounds more natural to the human ear—more like the roar of a waterfall than like the higher-pitched hissing sound of white noise. As a result, it is sometimes used to replace the white noise used in tinnitus maskers and in Tinnitus Retraining Therapy. More technically, pink noise is filtered to give equal power per octave or equal power per 1/3 octave. Since the number of Hz in each successive octave increases by two, this means the power of pink noise per Hz of bandwidth decreases by a factor of two or 3 dB per octave.