Ultrasound Techniques for Leak Detection

Leak detection of vehicle cabin interiors is an important quality inspection phase that typically has been handled with various time consuming, or potentially product damaging techniques. Leak detection in tank or pressure vessel applications is almost always a concern for gas or fluid containment in vehicles and in many other industries. Numerous techniques exist for the detection of leaks in these and other types of structures. When testing is required in a production environment, often the speed of leak detection is very important if all samples must be tested. The use of several ultrasound based methods for leak detection in vehicle cabins and pressure vessel applications is presented here. Ultrasound waves are typically classified as having spectral content greater than 20 kHz. In the case of leak detection in a production environment, frequently the ultrasonic spectrum is largely free from background noise content that dominates the audible spectrum. The method for the response measurement of ultrasonic signals presented here is with the implementation of high frequency microphones. The excitation methods presented here are an active method utilizing an ultrasonic emitter, a passive method relying on the passing of air through leak locations, and a vibro-acoustic method utilizing a small electro-dynamic shaker. The methods presented here have been tested for the existence of leaks in some structures, but have not been tested in this paper for the existence flaws and defects that may potentially lead to leaks in some structures after prolonged use.