Ultrasonic leak testers, sometimes called sonic, choked flow or turbulent flow, analyze the turbulent flow of a fluid across a pressure boundary that creates acoustic waves. These waves can be transmitted through the medium of the fluid itself, through the containment structure or through the air surrounding the containment structure. Because gas escaping through small holes generates ultrasonic sound, an array of ultrasonic sensors can be placed around the part. Computer control permits leak detection and, in certain circumstances, exact leak position may also be obtained, similar to dunk testing. Ultrasonic testing has become so widely used to test bearings, gearboxes and general mechanical inspection wear trends over time that it is often overlooked in leak detection. Part size is usually not a problem, nor is thermal variation. Arrays of sensors are used to pinpoint a leak. In some instances, pressure decay testing and mass flow testers have been integrated with ultrasonics to provide increased sensitivity. While this method has not been widely used, it has potential for larger parts.

In the future, leak testing will experience faster cycle times, improved reliability and validation. Leak testing will continue to be integrated into the assembly process and its accuracy and sensitivity will become higher.