Drum silencer optimized for NC-weighted insertion loss

A previous theoretical study1 shows that very light and highly tensioned membrane lining part of the duct walls with rigid cavity support can yield a high transmission loss (TL) over a broad band in the low to medium frequency range. Optimisation was carried out for the logarithmic bandwidth in which TL is greater than a pre-determined criterion value. The prediction TL was validated experimentally although the predicted optimal parameters were difficult to implement practically. In this study, a new cost function of total insertion loss (IL) with a frequency weighting with reference to an appropriate Noise Criterion (NC) curves is introduced. The new optimal design is compared with the previous under different loading impedance conditions. It is shown that a lower tension is required for the new optimized design. Detailed analyses are given for the modal response and spectral characteristics, together with discussions of the practical application of this device in noise control engineering.