Human analyzers and Helmholtz resonators: A prehistory of the sound level meter

Though Helmholtz resonators now find widespread application within silencers and sensitive acoustic spaces, they bear their name from a scientist who pursued neither of these ends. Rather, Hermann Von Helmholtz employed his namesake resonators as a convienent tool to analyze individual tonal components of complex musical sounds, essentially positioning the human observer as a signal analyzer augmented by a bank of tuned resonators comprising variable filters within the signal chain. In the lead up to the development of the sound level meter, both of these roles were ultimately replaced by electroacoustic technologies. However, this was not immediate, and echoes of Helmholtz’s apparatus were seen in such measurement techniques as Wallace Sabine’s aural determination of reverberation time, the resonant enclosue of the Tucker hot-wire microphone, and binaural methods of sound ranging during World War I. This presentation traces the physical and human antecedents to the modern electronic sound level meter, concluding with a few specialized cases where they can still find use today.