A fun fact is that the ability of a single transducer to function as both a speaker and a microphone is the basis for establishing an absolute measurement of so

A fun fact is that the ability of a single transducer to function as both a speaker and a microphone is the basis for establishing an absolute measurement of sound pressure. https://nvlpubs.nist.gov/nistpubs/jres/25/jresv25n5p489_A1b.pdf https://nvlpubs.nist.gov/nistpubs/jres/25/jresv25n5p489_A1b....