ASA S1.18-2018 PDF Download

This Standard describes procedures for obtaining the real and imaginary parts of the normalized acoustic impedance ratio of ground surfaces from in-situ measurements of the sound pressure levels at two vertically separated microphones using specified geometries and the averaged values of the difference between the simultaneous, instantaneous sound-pressure signals at the two microphones. It enables the user to either deduce parameters for a ground impedance model by fitting spectral data to templates or obtain values of the normalized specific acoustic impedance ratio of the ground entirely from measurements and independently of any model for the acoustic impedance of the ground surface except as a check on the validity of the resulting values.