Fig. 5
a, b are adapted from [36]
a Scheme of the air transparent soundproof window. It consists of transformed resonators and air filters. The diameters of air holes are 20 and 50 mm, respectively. The dimension of each cell is made of 150 mm × 150 mm × 40 mm and a thickness of 5 mm of transparent acrylic. It is arranged an array of 3 × 4 × 3 cells in parallel and series positions. b Transmission loss of the air transparent soundproof window. The red and blue lines denote 20 and 50 mm windows, respectively. The transmission loss is about 30–35 dB in the range of 400–5000 Hz with 20 mm window and about 20–35 dB in the range of 700–2200 Hz with 50 mm window.