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. The outcome of NSI has revealed silencer, oil sump and timing gear cover to be highest ranked sources in descending order.
Firstly silencer design optimization has been carried out using hybrid approach which combines experimental and simulation techniques with tail pipe noise as design criteria. The tail pipe noise prediction is done by uncoupled Boundary Element Method (BEM) analysis with source impedance and volume velocity as input boundary conditions. The silencer internal geometry is tuned to reduce the OEL to arrive at finalized design. Further structural optimization has been carried out using CAE tools on Timing Gear Cover (TGC) and oil sump supported by experimental modal analysis. The combined effort of structural and silencer optimization has yielded in 6 dB (A) noise reduction at OEL.