Techniques for assessing the wall condition and/or thickness from inside a pipe or manhole/chamber involve sending a wave or signal into the pipe/structure wall. Reflections, refractions and other wave disturbances potentially can provide information about the structural condition of the pipe wall, its thickness and whether voids are present outside the pipe/structure wall. The simplest of these techniques is simple sounding of the wall with a hammer. The tone of the sound made can vary with the condition of the wall and whether a void is present outside the wall. Measuring the rebound of the calibrated impact of a metal ball on a wall surface can provide additional quantitative information on the local condition of the wall. Acoustic wave methods can travel through the pipe wall and be reflected from the outer surface giving an indication of wall thickness and any wall thickness loss. A variety of electromagnetic methods are available for metal pipelines and are used frequently for assessment of oil and gas pipeline integrity.