Excessive levels of noise and vibrations are a major obstacle to the comfortable operation of industrial vehicles – but designing with the appropriate materials and techniques will help OEMS’ push on through
Off-highway vehicles are, by their very nature, noisy. Most industrial design team will face a constant battle to provide increased power and capability, while simultaneously furnishing the vehicle operator with a comfortable environment in which to work. The vehicle cab answers this need; and reducing the level of noise and vibration inside is important in achieving the objective. The main drivers for this activity are, of course, legislative requirements and the need to prevent temporary and permanent hearing loss.
How Sound Waves Travel in the Cab
The cab can be viewed as an enclosure. Sound travels from the source by vibrating the particles within adjacent and subsequent mediums and is propagated as waves of energy. Sound will enter the cab through any holes compromising the integrity of this enclosed space, and via transmission through the metal and glass panels. These panels will also respond to air borne sound incident on their surface, as well as vibration through cab mounts and other solid connections, exciting resonance in the panels and transmitting sound into the cab.
The interior noise level generated will be of a broad frequency range, while the level and frequencies at which the noise is most prominent will be a function of the original source, the mediums through which the sound passes, and the resulting environment.
That is to say, it will depend on the original sound power levels of the engine along with other sources and their operating conditions: the mass, size, shape and stiffness of the cab structure and how its different elements are connected; and the size and reverberation quality of the enclosure. The resulting noise level is further complicated by the weighting scale necessary to adjust for the way in which we perceive the sound, while the length of time of exposure to noise will also have a bearing on hearing loss. The operator may also feel vibration through the seat, floor and controls.