Measuring the force due to standard tapping machine and floor impedance for ASTM standards

The standard tapping machine used for the ASTM test standards on impact noise insulation does not have any provision to measure input force. A modified tapping machine with a force transducer was used for eight different residential floors, revealing that the force injected into the structure varies by approximately 37 dB. This variation is due to the combination of the tapping machine and the floor compliance. On one of the floors for the same test, the force injected due to the tapping machine varies by 2.6 dB for a single hammer. The floor impedance was also measured using accelerometers and the lightweight floor impedance is about 40 dB lower than heavyweight floors. The impedance varies by 20 - 30 dB throughout the frequency spectra for the four light-weight joist-framed floors. The authors propose that this injected force be measured, and an injected-to-radiated energy ratio be used to compare various floor-ceiling assemblies.