A total of 83 field impact insulation tests were performed using a Bruel & Kjaer calibrated tapping machine. The tests generally followed ASTM procedures. All measurements were conducted in the same building, using two adjacent receiving rooms constructed for the purpose of the tests. The floor-ceiling constructions tested consisted of a 7-in. concrete base slab, over which were installed a variety of resilient underlayments and finished floors. Tests were conducted with and without a resiliently suspended gypsum board ceiling. Results were extended at low frequencies to the 50-Hz third-octave band. However, measurements in the 50 to 80-Hz frequency range were often limited by background noise. The field impact insulation class (FIIC) results showed one of the resilient underlayments to be clearly superior to others under a ceramic-tile surface, but not as clearly superior under wood surfaces. The resiliently suspended ceiling improved FIIC ratings by 6 to 15 points, depending on the materials laid on the concrete slab. No tests were conducted on carpeted surfaces.