Example Procedures, Detecting Noises With Ultrasonic Tester
Rattling, knocking and humming noises
The low-frequency noises, muffled knocking noises (for example due to contact between the headliner and roof) or low-frequency humming noises create no or very few ultrasonic signals. In these cases, it is recommended to use the combo sensor which records and amplifies the audible noises and the ultrasonic sounds at the same time. This sensor is connected to the receiver through two connectors. Thanks to the wide range functionality and the option of higher sound amplification, it is possible to precisely locate the sound even if it is a low volume or behind instrument panels.
Headphones must be worn so that the whistling sounds coming from the device do not cause any confusion.
Noises from the engine compartment or body
Located with an ultrasonic sensor -1- or a sound pickup device with magnetic medium -1- They are mounted in pairs near the presumed source of the noise. Using the extension cords provided, it can be connected to the vehicle interior with a changeover switch on the receiver. The noise is evaluated during the test drive and the source is located by changing over and moving the sensors.
It is recommended to secure the sensors and cables with adhesive tape to avoid damaging these or other components caused by movement during the tests. It should be ensured that these are not mounted near any heat sources.
Locating small leaks in the intake manifold and in the exhaust system
Unsealed connections, loose wire clamps, porous or faulty vacuum lines as well as damaged seals can be clearly located with the receiver while the engine is running. A whistling/vacuum sound is heard through the headphones.
These small leaks could be the source of the noise at high engine speeds.
First, search the entire engine compartment using the receiver set at the maximum sensitivity with the headphones connected.
A higher ultrasonic level is created when there is a strong air stream. If this is the case, set the device sensitivity lower. After determining the approximate location of the source, the exact point of the leak will be located with the connected directional sensor or the pointed attachment.
Noises from mechanical components or bearings
Almost all friction between metal components generates ultrasonic sounds, which can be heard and seen with the tester.
To locate the noise source, first the receiver needs to be used with the headphones connected to determine the possible location of the source. The sensitivity should be set on the receiver, so that the noise can be heard well but is not too loud.
The highest LED display must lie within the center section (yellow LED). The noise is distinct in every case. Weaker signals are audible even if they are not shown. The closer the receiver comes to the damaged area, the stronger the received signal will become. To locate the noise source more accurately, connect the directional attachment (with the pointed attachment if necessary).
After closing in on the noise source, use the ultrasonic tester for structural vibrations, in which the point can contact the component and thus confirm that it is the location of the source.
Air leaks in the vehicle interior
To locate this leak, search with the receiver and the unidirectional attachment during a road test. Two technicians are required to do this in every case. Searching on the driver side during a test drive is dangerous and in this scenario, it is safer to perform a static test using the transmitter in the vehicle interior and the receiver in the exterior area. Using this method, air leak points can be located by scanning the door, window and panorama roof seals.
Air leaks in the vehicle interior are a possible cause of whistling noises or dynamic noises.
- The corresponding safety precautions must be followed during test drives where two technicians are required. One technician drives the vehicle, while the other conducts the test.
- The corresponding traffic regulations must be observed when driving on public streets. The test must never endanger the driving safety of the vehicle as well as the safety of other road users.