Experimental and analytical investigation on sound transmission loss of cylindrical shells with absorbing material

Abstract

In this study, sound transmission through a thin-walled cylindrical shell is investigated both<br><br>analytically and experimentally. A theoreticalmodel based on statistical energy analysis (SEA)<br><br>is developed in order to calculate the noise reduction and sound transmission loss of the cylindrical<br><br>shell. The procedure to obtain the parameters involved in the SEAmodel, such as radiation<br><br>efficiency and loss factors, is explained in detail. An experimental setup was constructed<br><br>in a reverberation chamber to evaluate the transmission loss of the cylinder using two experimental<br><br>methods. First the transmission suite method which includes measurements of the<br><br>sound pressure levels inside and outside of the cylinder usingmicrophoneswas used. Then the<br><br>sound intensity method was used in which the transmitted sound intensity is measured with<br><br>a sound intensity probe. The experimental results are compared with the analytical results<br><br>obtained from the SEA theory, which shows good agreement. By comparing both experimental<br><br>techniques, the transmission suite method is found to have advantages over the other<br><br>method at low frequencies. However, the sound intensity method is more applicable in the<br><br>mediumand high frequency regions between the ring and critical frequencies in order to predict<br><br>the noise transmission characteristics of the cylindrical shell. Another experiment was<br><br>conducted with absorbing materials placed inside the cylinder. The use of sound absorbing<br><br>material produced a significant reduction in the noise level in the cylinder specifically in the<br><br>high frequency range. The effects of the absorption coefficient on the acoustical behavior of<br><br>the cylindrical shell were also investigated theoretically.