Acoustic Impedance Measurements of Candidate Anechoic Liner Materials in Hyperbaric Conditions

Acousticians commonly account for the effects of variations in atmospheric pressure on the measurements they take, but the correction methods used are limited to small deviations from standard atmospheric conditions. Many unknowns remain surrounding acoustic measurement methods at pressures multiple times higher than ambient, including the applicability of sound-absorbing liner materials for anechoic chambers. This work will outline measurements of absorption coefficient of candidate liner materials for a hyperbaric anechoic chamber using a custom impedance tube designed to operate at elevated pressures. The variation in the absorption coefficient for a given material will be analyzed over a range of elevated pressures, characterizing any changes in behavior associated with the increase in density. These results will help to better inform future acoustics experiments and aid in the development of a hyperbaric anechoic chamber for aeroacoustic measurements of scaled multirotor aircraft configurations.