The improvement on the transmission loss of a duct by adding Helmholtz resonators

Abstract In this paper, the improvement on the acoustic transmission loss of a duct by adding some Helmholtz resonators is discussed. Therefore, the calculation on the transmission loss of a duct in a rigid wall by modifying the formula derived by Wilson and Soroka (Wilson G. P. and Soroka W. W., Approximation to the diffraction of sound by a circular aperture in a rigid wall of finite thickness. Journal of the Acoustical Society of America, 7965, 37(2), 286–297), its relating measurement and both the calculation of improved transmission loss of a duct by adding band-pass filters, and measurement of its involved transmission loss are included in this paper. The results of this study shows that agreement of the calculated transmission loss of a duct in a rigid wall with its related measurement is quite good at frequencies above 200 Hz, and the improvement of almost 28 dB on the transmission loss of the adopted duct at the frequency where the related transmission loss is to be improved can also be obtained when some appropriate Helmholtz resonators are added.

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