In 1940 while a professor at the University of Michigan invented the first practical ultrasonic testing method and apparatus.

The technology is not just used in quality control in factories to reject defective parts before shipment, but also revolutionized transportation safety.

For example, ultrasonic testing is used for safety maintenance inspection of railroad cars, particularly axles and wheels, aircraft, particularly fuselages, and other transportation vessels for material fatigue.

[10] Floyd A. Firestone in January 1925, demonstrated an electrical apparatus for determining the loudness of noise from bearings or other sources, before to the Society of Automotive Engineers meeting.

[11] The instrument was a modified audiometer consisted essentially by means of a Wente microphone combined with a sensitive electronic circuits and alternating current voltmeter;[12] therefore, this was the first time that a full electronic device was used to measure the noise level regardless the source type.