Ultrasound is sound with a frequency greater than the upper limit of human hearing. Although this limit varies it is approximately 20 kilohertz (20 kHz) in healthy young adults, therefore 20 kHz serves as the lower limit in describing ultrasound. The production of ultrasound is used in many different applications, typically to penetrate a medium and measure the reflection signature, but also to identify mechanical, electrical and airborne disturbances.
One of the more useful technologies is airborne ultrasound. Some of the common applications are leak detection in pressure and vacuum system, bearing & steam trap inspection, valve blow-by & pump cavitations, detection of corona in switch gear, compressor valve analysis, seals and gaskets integrity in tanks & pipe systems.
All operating equipment and most leakage problems produce a wide range of ultrasound. The high frequency components of these sounds are extremely short wave in nature, and a short wave signal tends to be fairly directional. It is therefore possible to isolate these signals from background noises and detect their exact location. In addition, as subtle changes begin to occur in mechanical equipment, the nature of ultrasound allows these warning signals to be detected early, before actual failure.
Airborne ultrasound instruments provide information two ways: qualitatively, due to the ability to "hear" ultrasounds through noise isolating headphones, and quantitatively, via meter readings. This is feat is accomplished by an electronic process called ”heterodyning”, which accurately converts the ultrasound sensed by the instrument into the audible range where users can hear and recognize them through the headphones. Although the ability to gauge intensity and view sonic patterns is important, it is equally important to be able to “hear” the ultrasounds produced by various equipment. That is what makes this technology so useful; it allows inspectors to confirm a diagnosis on the spot and gives them the ability to discriminate among various equipment sounds.
The reason users can accurately pinpoint the location of a particular ultrasonic signal in a machine or from a leak is due to its high frequency short wave. The ultrasonic environment is more conducive to locating and isolating the source of problems in otherwise loud environments.
Visit our Ultrasound Audio Gallery to hear the sample sounds and to see the Frequency & Time based graphs.