ネック部の粘性減衰を考慮したヘルムホルツレゾネータの設計

抄録

Pattern noise generated at contact surface of rolling tire should be suppressed to secure comfort of passenger in vehicle compartment. Frequency of pattern noise ranges around 1 kHz, therefore quarter wave length side branch is too long to design at tread surface of tire. Recently, Helmholtz resonator has been applied to reduce peak level of pattern noise. However, the neck part of the resonator is considerably narrow, hence acoustic dampings arising on the boundary between air and surrounding structure should be taken into account to predict quantitatively pattern noise level. In this study, air in the neck part of a Helmholtz resonator is considered as compressible viscous fluid and is modeled by Low Reduced Frequency (LRF) method. Analytical solution of a cavity with a small resonator is derived to save computational cost assuming that the neck part is one-dimensional tube and back cavity is rectangular acoustic field, By applying the derived model, the positions attached to the main cavity and the neck dimensions are designed to improve damping characteristics of Helmholtz resonator.