Theoretical Analysis and Measurement of Sound Transmission Loss in Louver Elements with a Sound Attenuating Function Using a Narrow Tube Array

Abstract

Sound transmission loss is relatively small in thin louver boards with a high aperture ratio. This study investigated louver elements with a sound attenuating function. Using narrow tubes, an array silencer was built into composite louver boards and a high aperture ratio was maintained. Several constructions for such louvers were prototyped, measured, and analyzed theoretically. Sound transmission loss was measured using four-microphone impedance tube. Then, sound transmission loss was calculated by a transfer matrix based on one-dimensional axial coordinate system analysis. The attenuation of sound in tubes should be calculated because a thin louver board must comprise narrow tubes. Therefore, an accurate propagation constant and a characteristic impedance based on two-dimensional analysis were introduced to enable theoretical analysis. The calculation results, including attenuation, and the experimental results had good coincidence. Moreover, the theoretical analysis confirmed that the silencer worked effectively and could be applied to silencer designs.

Keywords

• sound and acoustics
• noise control
• sound transmission loss
• array silencer
• side branch silencer
• silencer designs