The Study of the Acoustic Energy Loss in a Rectangular Duct Lined with Sound Absorption Materials

• Main Authors: Chen, Cheng Mine, 陳承明
• Other Authors: K.T.Chen
• Format: Others
• Language: zh-TW
• Published: 1998
• Online Access: http://ndltd.ncl.edu.tw/handle/60450614197075364966

碩士 === 國立臺灣大學 === 造船工程學系 === 86 === In this paper, the acoustic energy loss in a rectangular duct lined with sound absorption material is studied. First of all, a simplified model is derived by way of using a semi-infinite duct to simulate a generally used duct. When making both of the modal attenuation and calculation of total energy loss in the simulated semi-infinite duct in progress, might we be able to estimate the energy loss of sound propagation in an actual rectangular ventilating and air-conditioning ducts. Similarly, using computer Therefore, the following two parts of study are included in this paper: (1) the study on the acoustic characteristics of absorption material involved, its acoustic performance when lined in duct, the modal attenuation and total transmission loss in a rectangular lining duct. The result of the above study demonstrates that the acoustic energy loss as described is got greater when increasing the diameter and the thickness of lining fiberglass but reducing its bulk density and the width of lined duct. (2) The The result of this study clearly shows the fact that the calculated transmission loss of a semi-infinite lining duct is almost coincident with the measured insertion loss for the actual lined duct in experiment. The maximum discrepancy of the measured transmission loss at the outlet of a duct of two-wall lining from that of its simulated lined duct of semi-infinite length is not greater than 3 dB, and otherwise the same thing can provide further reference to both of the academic study and professional application.