Soundproofing glossary definition of narrow-band noise

narrow-band noise :

Noise in which the acoustic energy is concentrated in a relatively narrow range of frequencies. The spectrum will generally show a localized "hump" or peak in amplitude. Narrow-band sound may be superimposed on broad-band sound. If the narrow-band sound does not contain any significant discrete tones, the sound will generally lack a subjective quality of pitch or tonality.