Abstract
A new type of deep subwavelength acoustic metamaterial (AMM) absorber with 100% ventilation is presented in this study. The proposed ventilation absorber consists of coiled-up half-wave resonators (HWRs) and quarter-wave resonators (QWRs). First, the sound absorption and sound transmission performances for absorbers were analyzed considering the thermal viscosity dissipation. Then, the prototype with ten HWRs and three QWRs composed of acrylic plates was manufactured based on the theoretical model. The acoustic performance of the absorber was tested in an air-filled acoustic impedance tube to determine the sound absorption and transmission loss performances. Good agreement was found between the measured and theoretically predicted results. The experimental results show that the proposed ventilation AMM absorber is able to achieve sound absorption in a range between 330 Hz and 460 Hz with a thickness of only 32 mm (about 3% of the wavelength in the air). Furthermore, the sound transmission loss can achieve 17 dB from 330 Hz to 460 Hz. The main advantage of the proposed absorber is that it can be completely ventilated in duct noise control.
Highlights
The proposed sound absorber is composed of five pairs of symmetrical halfwave resonators (HWRs) formed by coiled-up space and, to improve the utilization of the remaining surface space in the upper level, three quarter-wave resonators (QWRs) containing a pair of symmetrical numbers with the designed length were installed in the remaining volume
A new type of ventilated acoustic metamaterial (AMM) absorber is proposed for simultaneous this study,and a new type of ventilated absorber is proposedwe for simult low-frequency noiseIn attenuation air ventilation
To predict acoustic performan deduced the theoretical model of the absorber, and, to validate the theoretical solutions, deduced theoretical model of theagreement absorber, was and,obtained
Summary
It is difficult to reduce low-frequency noise, since the thickness of these materials, by rule of thumb, is approximately a quarter of the operating wavelength [15], which would certainly cause the oversize of these materials in low-frequency noise reduction This can be attenuated with the use of acoustic metamaterials (AMMs), which have grown, after two decades of development, from the initial sonic crystals with effective negative elastic constants [16] to the current manifold structure AMMs that contain subwavelength structures and acoustic metasurfaces [17,18,19,20,21]. In this study, we propose a symmetry absorber that has both sound absorption and insulation Does it absorb noise with a deep subwavelength (0.03λ), but it is noise proof in the case of a 100% ventilation rate.
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