Langevin’s Ultrasonic Metrology

This article proposes that Paul Langevin should be considered the originator of ultrasonic metrology. He established the theoretical foundation for the use of radiation pressure for the measurement of acoustic power, by considering the energy density at a target in a beam. This approach was used for calibrating the ultrasonic transducers he helped to develop for submarine detection and underwater communications during the First World War (WWI). Within a decade, he developed two calibrated devices to measure acoustic power and average intensity, a torsion balance, and the first electronic power meter. He patented a piezoelectric non-resonant quartz hydrophone and a quartz probe to explore transducer surface vibration. Design criteria for the instruments included a rugged design that could allow measurements to be carried out not only in the laboratory but also at sea. Langevin was also influential in establishing an ultrasonics transducer laboratory in Toulon in 1923 where these instruments were used. New quartz pulse-echo transducer designs were developed and evaluated there, and performance certification was provided for manufactured transducers for both naval and civil systems. Early workers in ultrasonics recognized Langevin’s original and pioneering contributions, which were the enabling technology for modern ultrasonic metrology.