Study on Acoustic Characteristics of Lined Duct (Comparison between Analytical Result and Experimental Result)

Lined ducts have often been used to reduce the noises generated in a large wind tunnel and from an engine. Especially, the noise reduction has been strongly require compared to the experimental result to clarify the usefulness of the analysis. As a result, the acoustic characteristics of lined ducts could be predicted by the pred in the hospital, the office and the rail vehicle in accompany with the spread of the air conditioning. The acoustic characteristics of lined ducts has mainly been studied experimentally and a few analytically. According to these results, attenuation of lined ducts becomes large in a certain frequency range. Then this paper describes the theoretical analysis of sound field inside the duct in order to understand the phenomenon and theoretical result issent theory and theoretical results are useful to predict the attenuation of lined ducts. However it is very important to use the correct impedance of the absorbing materials.