The surface and near surface waves are coherent, traveling events which can be followed for substantial distances along with the receiving profile. The Cancellation can be accomplished by simply applying principles of directivity similar to those used in designing antennas for receiving radio waves. A different type if interference which is generally more difficult to cancel comes from incoherent noise, sometimes referred to as random noises. This is usually associated with scattering from near surface irregularities.

Incoherent noise is particularly common when the shot point overlies or is close to gravel, boulders, or vuggy limestone, all of which can cause scattering of the waves. The strength of the waves thus scattered depend inversely upon the distance of such materials from the shot. Sometimes the scattering occurs where steam banks and other topographic irregularities diffract energy from the shot and then return it to the recording line in the form of incoherent noise. Incoherent noise observed sat one point on the surface should by its very nature be entirely be unrelated to that at another point only a short distance away. This would not be the case with the coherent noise, where there would be a predictable relationship between the two signals.