A Perforated Plate with Stepwise Apertures for Low Frequency Sound Absorption

A perforated plate with stepwise apertures (PPSA) is proposed to improve sound absorption for low frequencies. In contrast an ordinary insufficient acoustic resistance and small mass, the stepped holes could match of air characteristic impedance also moderately increase mass especially at Prototypes made by 3D printing technology are tested in tube. The measured results agree well that prediction through theoretical numerical models. addition, absorber array plates presented extend bandwidth due introduced multiple local resonances.