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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. Objective of the present study is noise reduction on agriculture tractor by identifying and controlling key noise sources unaffecting performance parameters like power, torque and fuel efficiency to meet upcoming noise legislations. Noise Source Identification (NSI) is carried out to identify and rank airborne and structure borne noise sources. The airborne sources such as cooling fan, exhaust silencer and intake are evaluated using elimination method at tractor level. The NSI on engine is carried out separately in hemi anechoic chamber to identify the major noise radiating components by using noise and vibration measurement, sound intensity mapping tools.

Automotive seats play a vital role for improving the overall sound absorption inside the vehicle. To understand the acoustic performance of automotive seats in the passenger compartment of a vehicle, various types of seat assemblies were tested by the reverberation chamber method as per ASTM C423. The methodology has been developed to test the seats based on seats position in the chamber and minimum requirement of seats to evaluate the accurate sound absorption and Reverberation Time (RT). The effect of various seat cover materials like leather and cloth fabrics on the seat sound absorption and RT has been determined experimentally. Study of various cover materials (leather/vinyl and cloth fabrics) with PU foam for sound absorption characteristics has been carried out using simulation technique. The intrinsic parameters used as inputs in above steps are evaluated using specialized test rigs.

Diesel engine generator (DG) sets used in industrial plants and residential/official buildings cause serious noise problems if not (canopised) properly. Generally, DG set engines used are with rotational speed of 1500 rpm. In present study automotive diesel engine with 3000 rpm speed was converted for Genset application. Due to higher speed, engine noise levels and its cooling requirements were quite high. Objective of the study was to optimize the design of an enclosure for the said DG set to meet requirements of low noise and proper ventilation to comply MoEF legislative limits. A detailed Noise Source Identification (NSI) was carried out to identify and rank different noise sources. A Hybrid approach which consists of experimental DOE and simulation based on Boundary Element Method (BEM) was used for enclosure design. Design variables like enclosure dimensions, sound absorbing materials and louvers were used in optimization study.

Exhaust noise is the major noise source for the automotive vehicle contributing to its interior as well as exterior noise. The Transmission Loss (TL), noise reduction, Insertion Loss (IL) and radiated noise are the major characteristics used to describe the performance of a muffler in an automotive exhaust system. Out of these characteristics, Insertion loss and exhaust radiated sound pressure levels plays a significant role in muffler design as it is a measure of true performance of muffler along with engine/vehicle and very much useful for the designers to compare different silencer configurations. In present work, the sound source is modelled by acoustic impedance and volume velocity of the engine. Since it is difficult to estimate the sound source impedance of the exhaust by measurements either with direct or indirect methods as both are prone to errors and difficult to implement, the empirical equations are used to define exhaust source, to have reasonable accuracy.

With the stringent legislative requirements for noise in automobiles, gensets etc., the concern for properly designed silencers for specific applications is increasing. Optimized design of silencer requires an integrated study of acoustical and engine performance viz. Insertion loss and backpressure. However, the insertion loss itself depends upon engine characteristics geometry indicated by the transmission loss, flow induced noise, type of silencer - reactive, absorptive, hybrid, etc. Most of the work till date covers the acoustical and engine performance in isolation rather than in an integrated fashion due to the multidisciplinary nature of the problem. The objective of this study is to develop an integrated methodology to predict the performance of the silencer at the design stage resulting in an optimized time and cost effective design. In the present study, the acoustical and engine performance of silencer was predicted using FEM/BEM and CFD techniques.