Ruído, vibração e aspereza

501-25-94 Body Repairs - General Information 501-25-94 DESCRIPTION AND OPERATION The test device has six different channels for noise diagnosis. This means that six microphones equipped with clamps can be attached to different components on the vehicle. The emitted or transmitted solid-borne sound will be transferred from microphone to the headphones. There is an amplifier between the microphone and the headphones at which the signal strengths and the corresponding channel can be set. Only the noises from one microphone are transferred to the headphones. Each channel is color-coded on the clamp, cable and amplifier. NOTE: In order to be able to relate the positions of the different microphones during the test process, they are entered in a special test sheet according to their colors. Microphones, clamps and cables must be carefully routed and attached. Test process (example for transmission noise): ‡ Attach microphones to various positions on the transmission or mountings. This first allows the source of the noise to be determined, and then the possible transfer routes. ‡ A road test can be performed after all the clamps have been attached to the vehicle and all the cables connected to the amplifier. ‡ Firstly, all the channels are switched through one after the other in neutral, to check the operation of the different channels as well as the noise level in neutral. ‡ During the road test, all channels are listened to in the different gears, engine speeds, vehicle speeds and loads. This procedural method permits unambiguous diagnosis of the cause of the noise and the route of the noise until it enters the bodywork structure. ‡ The characteristics of the noise which is the cause of the concern should match those of the noise which is heard. This means compare the sound. ‡ Depending on the input signal level, there may be a great deal of difference in the noise level in the individual channels. ‡ Always set the amplifier volume to zero before switching to another channel. ‡ In order to be able to make any comparisons, the volume settings of the different channels must be recorded on the test sheet.