High-Temperature Acoustical Properties of Materials

Abstract

The normal absorption coefficient and the normal specific acoustic impedance of the following several materials were measured as a function of temperature for temperatures up to 1500°F and frequencies up to 1800 cps. The specific acoustic impedance of all materials measured increased with temperature and caused a variation in absorption which is dependent upon the variation of the specific acoustic impedance of the material relative to the specific characteristic impedance of air. An acoustic impedance tube with the sample holder inserted into an electric furnace was used for the measurements. Both longitudinal and vertical temperature gradients were present in the tube. Empirical corrections were made to the data, but the detailed effect of the gradients on the measured absorptions and impedances has not yet been completely determined. (This research was supported by Wright Air Development Center).