组合型亥姆霍兹通风吸声体低频宽带吸声特性研究

Characteristics of Low-frequency Broadband Sound Absorption of Combined Helmholtz Ventilated Absorbers

为解决低频段通风吸声效果差的问题,提出一种亚波长厚度的颈部嵌入式亥姆霍兹通风超材料吸声体,该结构由中央通风开放区域和周围布置的多谐振器两部分组成。通过精确设计每个共振单元,使吸声体在445~678 Hz频率范围内具有优异的吸声特性,吸声系数均在0.85以上。该结构厚度为40 mm,仅是445 Hz波长的1/20。分析嵌入颈部的吸声机制,指出结构在颈部位置处,会具有很强的黏性来耗散声波能量,且共振频率随着颈部嵌入的长度增加而向低频偏移。随后,通过实验验证通风吸声体的传递损失与计算结果符合良好,目标频段内传递损失平均提高6dB。因此,该功能结构的通风吸声体材料为在低频域实现高吸声能力的可行性得到验证。

In order to solve the problem of poor ventilation and sound absorption effect in low frequency band,a subwavelength thick neck embedded Helmholtz ventilation metamaterial absorber was proposed.This absorber consists of a central ventilation opening and peripheral arranged multi-harmonic oscillators.Through precise design of each resonant unit,the acoustic absorber exhibits excellent sound absorption characteristics in the frequency range of 445-678 Hz,and the sound absorption coefficients are all higher than 0.85.The thickness of the structure is 40 mm,which is only 1/20 of the wavelength of 445 Hz.The sound absorption mechanism embedded in the neck was analyzed.It was found that the structure has strong viscosity to dissipate sound wave energy at the neck position,and the resonance frequency shifts to lower frequency side with the increase of neck embedding length.Subsequently,it was verified through experiments that the transmission loss of the ventilation sound absorber is in good agreement with the calculated results,and the average transmission loss within the target frequency band can be increased by 6 dB.Therefore,the feasibility of the ventilation sound-absorbing material with this functional structure to achieve high sound absorption capacity in the low-frequency domain has been verified.