The attenuation is higher with increasing wave frequency and soil depth. Coating and insulation also increases the wave attenuation. It will be higher than a bare or painted pipe. The below data were plotted to show the soil effect on wave propagation. The top plot shows the data of 20- kHz torsional mode from a 4.5-inch-OD bitumen coated pipe without soil cover. The bottom was acquired after a 3.2-ft soil covering. The attenuation was significantly increased due to guided-wave energy leakage to the soil.