The Physics of Opera Singers

What is it about opera singers that allows them to be heard above the orchestra? It’s not that they simply singing louder. The qualities of sound have to do with the relationship between the frequency (pitch) of a sound, represented in a unit of measurement called hertz, and its amplitude, measured in decibels, which the ear perceives as loudness. Only artificially produced sounds, however, create a pure frequency and amplitude (these are the only kind that can break glass). The sound produced by a violin, a drum, a voice, or even smacking your hand on a table, produces a fundamental frequency as well as secondary, tertiary, etc. frequencies known as overtones, or as musicians call them, harmonics