Estimation of temperature gradient effects on the normalized surface impedance of soils

Abstract

Ground impedance measurements are used for sound propagation predictions and to determine soil properties. Solar heating of the ground leads to significant temperature swings and gradients in the near surface soil. The equations of thermoacoustics are applied to estimate the magnitude of the temperature effects on the impedance and develop an approximate equation for the adjustment of measured impedance. Ambient temperature effects are shown to be significant; temperature gradient effects in soils are negligible. The theory is applicable to noise control applications where larger gradients may occur in sound absorbing materials.