All equipment and mechanical, electrical, steam, air, etc. systems when they are in operation, they emit low frequency sounds perceptible by the human ear and high frequency sounds that are imperceptible to the human ear. These sounds can be normal if they are within the parameters established by the designer and the manufacturer of the equipment or system, or they can indicate failures in precise areas if they deviate from those parameters.
The ultrasound equipment detects a small range of high frequency ultrasonic signals and translates them electronically into the range audible to the human. Ultrasound equipment allows us to listen to what the human ear can not detect. Because it is directional, the intensity of the sound does not travel far from the origin making the detection of the problem very fast and precise.
But although the equipment provides us with the sounds, they must be identified and analyzed in order to determine if there is a problem and if it exists, what is the seriousness of it. For this it is necessary that whoever hears and analyzes those sounds is an experienced person, with knowledge in the ultrasound equipment and in the systems and equipment that are inspected. This is the function of the Ultrasound Inspector.