Impedance deduction from broad-band, point-source measurements at grazing incidence

A new method has been developed which derives surface impedance from measurements of excess attenuation at grazing angles over locally reacting surfaces. The technique uses classical sound propagation theory to fit complex surface impedance to acoustic measurements. Short range excess attenuation measurements have been made over dry sand, glass beads and felt. Two versions of the impedance deduction technique and two non-invasive measurement methods are presented. The results obtained using both procedures are shown to be consistent with each other and with standing wave tube data.