Acoustic radiation from a plate into a porous medium

Abstract A theoretical model is developed for acoustic radiation from a plate into a porous medium. The medium is modelled as an equivalent fluid with complex density and complex wavespeed. It is found that radiation from a finite plate is dominated by area radiation at all frequencies, unlike the case for radiation into air where it is only area dependent above the critical frequency. Although particle motion is similar to that for radiation into air, the circulatory motion below the critical frequency still results in energy loss from the plate due to dissipation within the medium. As radiation is area dependent at all frequencies, a simpler model based on radiation from an infinite plate is also developed. This gives the same answer as radiation from a finite plate to leading order. Plate losses measured for radiation into a finite thickness layer of porous material show good agreement with predicted results.