Variation in sound attenuation performance due to changing duct length and installation of sound absorbing materials

Yuka Yamashita, Kunihiko Ishihara

Duct, Noise, Sound absorbing material, Sound attenuation performance, Acoustic natural frequency

Ducts are widely used in buildings, and various types of air conditioning ducts and exhaust ducts are also used in the medical field. It has been reported that these ducts generate noise, which affects the quality of sleep and causes various physiological disorders and loss of performance when awake or at work. In this study, we evaluated the sound attenuation performance (reduction degree of resonance peak value) by extending ducts, installing sound-absorbing materials, and changing the shape of ducts as countermeasures. As a result, the attenuation performance due to the extension of the duct decreases linearly with length, and the degree of decrease is independent of the cross-sectional shape. Furthermore, as the amount of sound-absorbing material increases, the sound pressure level decreases logarithmically. As the resonance mode order increases, the peak value becomes smaller, and if the quantity doubles, the peak value decreases by about 3dB, consistent with the so-called room acoustics theory.

https://dx.doi.org/10.31873/IJEAS.11.05.07