ESTIMATION OF TEMPERATURE-GRADIENT EFFECTS ON THE NORMALIZED SURFACE IMPEDANCE OF SOILS

Ground impedance measurements are used for sound propagation predictio ns and to determine soil properties. Solar heating of the ground leads to significant temperature swings and gradients in the near surface s oil. The equations of thermoacoustics are applied to estimate the magn itude of the temperature effects on the impedance and develop an appro ximate equation for the adjustment of measured impedance. Ambient temp erature effects are shown to be significant; temperature gradient effe cts in soils are negligible. The theory is applicable to noise control applications where larger gradients may occur in sound absorbing mate rials. (C) 1997 Acoustical Society of America.