Microperforated Panel and deep subwavelength Archimedean-inspired spiral cavities for multi-tonal and broadband sound absorption

In recent years, metamaterial-structures and Microperforated panel (MPP) absorbers have been proposed as a valid alternative to porous materials for sound absorption in the low frequency range. However, high broadband cannot be achieved range required some engineering applications where large thicknesses of are unsuitable. this work, deep subwavelength hybrid parallel-arranged MPP Archimedean-inspired spiral (AIS) absorber is obtain at (i.e. 400–2000 Hz). The properties investigated using an equivalent electro-acoustic model parametric analysis performed optimise geometric parameters device desired Two parallel arranged MPPs AIS structures were designed achieve ranges between 550–1650 Hz 380–1250 Hz, with total thickness less than 1/28 wavelength (24.3 mm). addition, arrangement double layered also considered wider 480–2800 prototypes then fabricated tested impedance tube evaluate normal coefficient via Transfer Function method (TFM). Experimental results show good correlation analytical models, above 60% over respective ranges. Moreover, peaks occur resonance frequencies higher harmonics structures, measured values 95%. shown by makes suitable many acoustic applications.