The diesel generator sets are widely used in public areas and corporate buildings as electric source or backup. Hence it is necessary toreduce the noise produced by diesel engines of generator. Noise of diesel engine can be reduced by using muffler. Design and optimization of muffler isdone by providing perforations. Perforation design is optimized for maximum transmission loss by varying three factors, i.e. perforation diameter, porosityand length over which perforations are applied. For optimization, Taguchi method is used. Acoustic performance of muffler is estimated by commercialFEA software.