Historical
ANSI/ASA S1.18-2010
American National Standard Method for Determining the Acoustic Impedance of Ground Surfaces (with associated computer application ZIP file)
This Standard describes procedures for obtaining the real and imaginary parts of 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 extends and revises the template method given in the 1999 edition to enable the user to 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
Acoustical Society of America [asa]