1.1.5.1.2.4 Noise propagation in vehicles Examples: Noise from the drive motor. Pass directly through the air. The vibration is transmitted from the motor to the car body and then radiated to the cab in the form of sound waves. 1.1.5.1.3 Vibration Technology Human ears can't hear the vibration wave with frequency lower than 20Hz (low frequency) or higher than 20,000Hz (20kHz: high frequency). The motor adopts flexible installation, and it can vibrate up and down when driving on uneven roads. When the flexible installation fails, the vibration will be transmitted from the motor to the body and then to the cab. The following rules apply:
Automotive technology is not only concerned with audible low-frequency vibrations but also with inaudible high-frequency vibrations. Low-frequency vibrations are usually visible. High-frequency vibration can be heard or felt through the floor and steering wheel. 1.1.5.1.3.1 Resonance Every object has its natural frequency of vibration. A system that vibrates an object at its natural frequency will resonate. 1.1.5.1.3.2 Damping If a damper is connected in parallel with the spring, the vibration of the object will be attenuated. Automobile shock absorbers are made according to this principle. Damping affects the resonance of an object or system.
Through the function of the shock absorber, the vibration is attenuated to achieve the purpose of eliminating the vibration of the vehicle body. The car shock absorber is actually a damper, which attenuates the vibration of the car body in a damping manner. 22 Project Part name Description 1 - Airborne noise 2 - Car body noise