The Slab Impulse Response (SIR) method is used primarily to identify and map subgrade voids below slabs-on-grade, although it also sees use in general condition evaluation of structural elements. This method is excellent for evaluating the repair of slab subgrade support conditions by comparing the support conditions before and after repairs. The SIR method is often used in conjunction with Ground Penetrating Radar for subgrade void detection and mapping.

The SIR method has been used on slabs of a wide range of thicknesses, but is most effective on thinner slabs (less than 12 inches thick). The method is generally limited to slab thicknesses of less than about 20-24 inches in thickness for most applications.

An alternate application of the SIR method is in the general evaluation of the condition of concrete structures. In this application, the method is used to look for low-stiffness areas associated with hidden damage such as honeycomb, void, and cracking. The method can be used for a fast evaluation of structural conditions, with a more detailed investigation than performed with Impact Echo or Ground Penetrating Radar.