Essay On Noise And Vibrations

Reducing Interior Noise in Car Using Viscoelastic Damping

Nur Farahie Binti Juhari

Department of Mechanical and Manufacturing Engineering, Universiti Putra Malaysia, Selangor

Abstract

1. Introduction

Noise and vibration are important aspects in order to ensure the comfort of drivers and passengers in transportation vehicles. Noise can be defined as any unwanted sounds which mean any sounds that particularly loud ones, that disturb people or make it difficult to hear wanted sounds. Noise and vibration energy is transmitted from the sources to the drivers and passengers through two paths which are airborne and structure-borne paths. The amount of noise and vibration reaching people are different from one another. The interior noise of vehicle also depends upon the type of vehicle and the occupied space considered. The noise of a vehicle is due primarily to the engine, transmission system and accessories, road excitation, and air buffeting. The noise is produced by complex vibrations of the outer surfaces of the

The viscoelastic material is sandwiched between the substrate that is vibrating and a relatively stiff constraining layer. The purpose of the constraining layer is to produce a shearing action with the viscoelastic layer as the composite sandwich vibrates. Constrained layer damping is used more to reduce vibration than to attenuate noise. The extensional damping coating and the viscoelastic layer of the constrained system are based on polymeric materials, which are selected because of their relatively high mechanical loss factors under the required conditions. The effectiveness of the constraining layer depends directly on its modulus and on the relative thickness of the viscoelastic layer and the constraining layer. These parameters are optimized based on damping characteristics, cost, added weight, durability of treatment in the expected service environment, and