A low-frequency anechoic coating under high hydrostatic pressure by pressure balancing strategy

It has always been a challenge to develop low-frequency anechoic coatings under high hydrostatic pressure. Based on active pressure balancing strategy (APBS), the airbag embedding in Helmholtz resonator model is proposed to achieve low-frequency and broadband sound absorption under high hydrostatic pressure. Compared with some existing pressure resistance schemes, the proposed anechoic coating has a thinner and lighter structure, lower sound absorption frequency band, and can withstand higher pressure. The proposed anechoic coating achieves sound absorption coefficient larger than 0.5 within the bandwidth of 24.5 similar to 1000 Hz under pressure of 0.1 MPa, and within the bandwidth of 73.6 similar to 1000 Hz under pressure of 5 MPa. The thickness of 10 mm is less than 1 parts per thousand of the incident wavelength at 100 Hz. The proposed model provides a new solution to the problem of improving low-frequency sound absorption performance of the anechoic coating under high hydrostatic pressure.