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In general, in-cabin booming noise is low frequency (20 Hz∼300 Hz) phenomenon which excites the cabin structure mainly due to excitations from the powertrain, exhaust system, road loads, etc. When a vehicle drives over road seams or a bumpy surface, low-frequency drumming noise is generated, causing driver discomfort. The generation of drumming noise is due to road irregularities, transferred and amplified through the vibration characteristics of the suspension, body frame, and body panels, as well as the acoustic characteristics of the vehicle interior. It is therefore difficult to take measures to get rid of drumming, after the basic vehicle construction has been finalized. The regular practice in vehicle development is finite element method (FEM) to obtain acoustical transfer functions of the body, and multi body simulation to get suspension load characteristics. The full vehicle simulation needs more time for analysis and extracting data.

Generally three cylinder engines due to less reciprocating masses are said to be more fuel efficient. Nevertheless, NVH problems caused by inherent imbalance forces and couples remain as draw back. NVH refinement levels can be improved by stiffening of the engine structure, material change, optimal design of the crank train, control of cylinder to cylinder pressure variation, etc. The objective of this study is to reduce the radiated noise of diesel engine by 2-3 dB (A) in the frequency range up to 4 kHz. Simulation and test based approach was demonstrated for reducing radiated engine noise. The NVH performance of the baseline engine has been evaluated using CAE simulation tools. Radiated noise from the critical components like oil sump, crank pulley and timing cover has been predicted and the critical modes having severe effect on radiated noise levels of the engine has been identified.

The vibration and acoustic behaviour of the internal combustion engine is a highly complex one, consisting of many components that are subject to loads that vary greatly in magnitude and which operate at a wide range of speeds. The interaction of these components and the excitation of resonant modes of vibration is a major problem for the powertrain engineer when optimising the noise and vibration characteristics of the engine. This paper summarises a study that has been undertaken to assess and optimise the dynamic behaviour of a current production diesel engine with the objective of reducing radiated noise from the engine. The dynamic behaviour of the diesel engine has been assessed using simulation tools. The dynamic analysis will predict the forces and displacements at each of the nodes of the model by forced response analysis. Predicted results and experimentally measured values were found to be in close agreement.

The automotive market has seen a steady increase in customer demands for quiet and more comfortable tractors. High noise at Operator Ear Level (OEL) of tractor is the major cause of fatigue to the operator. With growing competition, and upcoming legislative requirement there is ominous need for the agricultural tractor manufacturers to control noise levels. The objective of this study is noise reduction on agricultural tractor by stiffening sheet metal components. The design and analysis plays a major role for determining the root cause for the problem. Once the problem and its root cause were well defined, the solution for addressing the problem would be made clear. The engine excitation frequency and Sheet metal Components such as fender and platform natural frequency were coming closer and are leading to resonance.

Tractor operators prefer to drive more comfortable tractors in the recent years. The high noise and vibration levels, to which drivers of agricultural tractor are often exposed for long periods of time, have a significant part in the driver’s fatigue and may lead to substantial hearing impairment and health problems. Therefore, it is essential for an optimal cabin design to have time and cost effective analysis tools for the assessment of the noise and vibration characteristics of various design alternatives at both the early design stages and the prototype testing phase. Airborne excitation and Structure Borne excitation are two types of dynamic cabin excitations mainly cause the interior noise in a driver’s cabin. Structure-borne excitation is studied in this paper and it consists of dynamic forces, which are directly transmitted to the cabin through the cabin suspension. These transmitted forces introduce cabin vibrations, which in turn generate interior noise.