S, S. and Solanki, N., "Automotive Exhaust Muffler Design, Development and Study on Attenuating Whistling Noise," SAE Technical Paper 2013-26-0099, 2013, doi:10.4271/2013-26-0099.
This technical paper presents a study to eliminate 6.5 kHz to 8.0 kHz abnormal whistle noise created by the exhaust at engine rpm ranging from 2000 rpm to 4000 rpm. The abnormal noise to a customer has a high level of repeatability during highway driving. Vehicle level experiments were carried out to root cause the noise source and identify optimization, which will not impact other parameters like exhaust back pressure, emission and vehicle pass-by noise. The study was focused on perforated pipes in mufflers internals with different perforation patterns, hole sizes, hole shapes and addition of glass fiber mat.