Author(s)

Hiromitsu Hamakawa¹, Hiroki Matsuoka², Taiki Yamai², Kenta Asakura³, Toru Otsuru⁴, Reiji Tomiku⁴, Eru Kurihara¹, Hidechito Hayashi⁵, Eiichi Nishida⁶

¹Department of Mechanical Engineering, Oita University, Oita, Japan.
²Graduate School, Master’s Program of Engineering, Oita University, Oita, Japan.
³Torishima Pump Mfg. Co., Ltd, Takatsuki-shi, Osaka, Japan.
⁴Department of Architecture, Oita University, Oita, Japan.
⁵Department of Mechanical Engineering, Nagasaki University, Nagasaki, Japan.
⁶Department of Mechanical Systems Engineering, Shonan Institute of Technology, Fujisawa-shi, Kanagawa, Japan.

The present paper focuses on the effect of air jets through a perforated thin plate on the characteristics of an acoustic absorption coefficient. We measured the flow rate, internal pressure, acoustic pressure, and transfer function by using an improved acoustic impedance tube. The normal incidence absorption coefficient was calculated from the measured transfer function using transfer function methods. As a result, the frequency characteristics of the acoustic absorption coefficient against the frequency showed a maximum value at the local frequency. The peak frequency of the acoustic absorption coefficient depended on the thickness of the background air space and the thickness of the perforated plate. As the flow rate increased through the micropores, the peak level of the acoustic absorption coefficient also increased until a flow rate of 80 l /min. As the flow rate further increased, the peak level of the acoustic absorption coefficient decreased and that of the high frequency band increased.

Acoustic Absorption Coefficient, Perforated Plate, Cavity, Micropores, Air Jets, Acoustic Impedance Tube

Hamakawa, H. , Matsuoka, H. , Yamai, T. , Asakura, K. , Otsuru, T. , Tomiku, R. , Kurihara, E. , Hayashi, H. and Nishida, E. (2015) Acoustic Absorption Characteristics of Perforated Thin Plate with Air Jets and Cavity. Open Journal of Fluid Dynamics, 5, 1-9. doi: 10.4236/ojfd.2015.51001.