This paper presents a new design of a perforated plate-type acoustic metamaterial (PAM) to evade the influence of membrane pre-tension on the acoustic performance of metamaterials and to enable air ventilation while achieving the designated sound insulation. The study embarks on the analysis of sound insulation mechanism of typical perforated membrane-type acoustic metamaterials (MAM), and discloses that sound transmission loss (STL) peaks of a perforated MAM are due to the strong wave interference between the sound sources transmitted through the orifice(s) and the membrane(s). The sound insulation mechanism is explored further in the study by an acoustic impedance analysis of a perforated metamaterial using an electro-acoustic analogy in the latter part of the paper, and the result confirms that the STL peaks of a perforated PAM (or MAM) is indeed the outcome of a strong sound interference. The study also presents an experiment test and a finite element simulation on the sound transmission of a perforated PAM based on the new design. The results confirm that the new perforated PAM can yield a good broadband STL at relatively low frequencies.

Metamaterials, MAM, PAM, Perforated, Transmission loss