A Brief Discussion on Noise Reduction Treatment of Construction Machinery Cabs

The cab of construction machinery is a space for operators to work and move around. Besides having a good field of vision, sufficient rigidity and strength, it must also ensure a comfortable and convenient operating environment, meeting the requirements of human-machine engineering and facilitating the efficient and reliable work of operators.

The sound insulation and noise reduction capabilities of the cab directly affect the comfort and labor efficiency of the operators. According to relevant data analysis, the noise in the cab of construction machinery comes from engine transmission noise, chassis transmission noise, working device noise, road noise and friction sound, etc. The noise reduction methods are roughly: vibration prevention, sound insulation and sound absorption. The following is a simple analysis and discussion of three noise reduction approaches.

1. Anti-vibration. There are roughly two types of vibration prevention: one is to prevent the large covering parts from receiving 1-2 low-frequency vibrations over a wide range, and the other is to prevent high-frequency vibrations over a small range. The former can adopt measures such as changing the curvature, increasing the tensile ribs, and enhancing the rigidity of the covering parts. The latter can enhance the vibration reduction capacity by using anti-vibration materials. A common method is to add a sandwich structure of anti-vibration materials between the steel plates, and achieve a higher vibration reduction capacity through the shear deformation of the middle layer. This method should be especially adopted on the cab panel and floor close to the engine side. There are two ways to make sandwich components: One way is to add anti-vibration materials between the punched steel plates; Another approach is to adhere a resin layer or an asphalt-based anti-vibration plate onto the steel plate. Appropriate elastic and damping elements should be installed between the cab and the chassis to reduce the vibration of the cab structure and the secondary noise generated therefrom.

2. Sound insulation. To prevent engine noise from penetrating, sound insulation materials are mainly used on the inner panels of the cab close to the engine. For the gaps around the hoses, wires and steering columns passing through the cab, to prevent sound transmission through the gaps, sealing treatment should be carried out around the holes.

The driving noise on the road surface and the noise from the engine exhaust device are mainly transmitted through the cab floor. Therefore, the floor should adopt a double-wall structure. The air layer in the middle can act as a spring, and the sound insulation capacity will be greatly reduced. Synthetic foam materials or surface anti-vibration materials need to be used in the middle layer.

3. Sound absorption. Sound absorption is the use of materials and structures capable of absorbing sound energy to absorb a portion of the sound energy along the noise transmission path, thereby reducing the noise that reaches the operator's side. To reduce the noise from the engine, install sound-absorbing materials such as fiberglass, blankets and foam on the side panels of the cab close to the engine and the inner side of the engine hood, and adjust the sound absorption intensity and characteristics according to the thickness and density of the materials.

The interior materials for the other inner surfaces of the cab should not only be aesthetically pleasing and soundproof but also have sound absorption properties. Sound-absorbing materials are mostly porous materials, such as glass fiber, foam plastic, blankets, etc.

The above three noise reduction approaches are the commonly used noise reduction methods by various manufacturers at present. They are feasible and fully meet the requirements for indoor noise and radiated noise stipulated in the EU CE Directive.