acoustic perfume

:  the effect created when a constant pleasant or inoffensive background sound (such as music, white noise, or the sound of a fountain) is used to drown out unpleasant or distracting noises (as in an office or a public place); also :  the sound itself Early visitors waxed enthusiastic about the relief it provided from the din of the streets, and the “acoustic perfume” of the park's waterfall. — George Prochnik, New York Times, 13 Dec. 2009