Input force and floor impedance measurement for the standard tapping machine and the standard impact ball

Abstract

The current ASTM and International Standards Organization (ISO) standard im- pact test method for floor-ceiling assemblies does not require the test engineer to measure the input force during the impact. A standard tapping machine or a standard impact ball is used for these tests, but these input sources usually do not have any provision to measure the input force. In this work, the input force of these impact methods was measured on seven different assemblies, and a modal hammer was used as a “control” source. The input force and average floor impedance were measured and compared to each other. The peak input force levels due to the tapping machine vary by approximately 38 dB from one floor to the other, and the frequency excitation bandwidth varies widely based on the type of floor construction. This shows that there is a need to measure the input force and scale the output sound quantity with the input force to get a frequency response function (FRF)-like quantity to compare different floor-ceiling assemblies. For the impact ball, the variation in low-frequency input force levels is almost non-existent, but the impact ball has a poor measurement signal-to-noise ratio above 80 Hz one-third octave band. The impedance measured using the impact ball matches closely with the control impedance measured using the modal hammer.