(1. School of Automotive Engineering, Chongqing University, Chongqing 400715, China) （2. College of Intelligence Science, National University of Defense Technology, Changsha 410073, China) (3. College of Engineering and Technology, Southwest University, Chongqing 400715, China)
How to achieve low frequency broadband sound absorption has always been one of the urgent problems in the field of noise control engineering. The rapid development of acoustic metamaterials in recent years has provided new solutions for this. In this paper, widening the single peak absorption bandwidth and introducing the second-order absorption peak was effectively combined to obtain a low frequency broadband sound absorption metamaterial based on the combined micro-perforated plate. Then both the theoretical and numerical simulation models of the structure of combined micro-perforated plate were established. The theoretical results agreed well with the numerical calculation results, which verified the accuracy of the proposed structure. The sound absorption structure can produce double absorption peaks in the low frequency range, and the value of the absorption peak was close to quasi-perfect sound absorption. At the same time, it had two wider absorption bandwidths, and the structure thickness fell in the range of subwavelength scale, exhibiting good low frequency broadband sound absorption property. Finally, through strict parameter design, a continuous sound absorption band was obtained in the range of 250~900 Hz by coupling only two sound absorption units. The average sound absorption coefficient of the structure reached 0.86, which corresponding to a maximum thickness of 70 mm. Holding the feature of excellent low frequency broadband sound absorption property and rich adjustability,the sound absorption structure will have certain application prospects in the field of noise control engineering.