This tool is designed to locate the source of noise emanating from a failing mechanical component, such as a bearing, worn camshaft or follower, slipping alternator drives etc. It has the advantage over traditional audible methods such as a stethoscope or even the use of a long screwdriver in that it not only “hears” the frequencies within the scope of human senses that reveal a failed component but can also detect the ultrasonic frequencies that emanate from a failing component which are generated long before they become audible to us, and translates these frequencies into a sound we can hear in the headphones. The solid extension piece, included in the kit, is perfect for locating mechanical noise.
This ultrasonic noise has the advantage in that it is very directional and also attenuates rapidly, this makes pin-pointing the source a more precise exercise. 
A very important feature of this tool is the ability to trace air, vacuum and exhaust leaks  which are generated by turbulence created by escaping gas, again often inaudible to us. This tool can detect a gas leak down to .005” which may be too small to see with a smoke test, for instance a leaking air suspension component.. The included extension tube is used to gain access under inlet or exhaust manifolds. It is also possible to detect a fluid restriction, e.g. partially blocked fuel line, by the noise generated by turbulence at the source.    
This tool also comes with an ultrasonic signal generator which can be placed inside the vehicle cabin to locate the source of wind or water leaks from door or window seals, sun roofs, boot lid seals etc. 
The included extension tube allows for access into restricted areas to pin-point the source. 
This can be much quicker and much more convenient than the traditional water test.
The kit includes:- ultrasonic receiver, ultrasonic transmitter, headphones, solid extension and an extension tube, packed in a protective case.