Numerical and experimental investigation of the narrow-band impact sound insulation of layered floors

Measurement results of the impact sound insulation of (floating) floors are generally limited to one-third octave bands. As a consequence, detailed information on modal behavior and on the influence of the impact source, are largely lost due to band-integration. To this end, narrow-band measurements are performed on five different layered floors. Various tapping machine locations are considered and the results are averaged over several receiver positions for each tapping machine location in order to reduce the influence of the spatial distribution of the sound pressure in the receiver room. A new prediction model for impact sound transmission, termed the modal TMM, or mTMM, is used to interpret and investigate the measurement results. This prediction method includes a detailed source model and accounts for the finite dimensions of the layered floors. The measurement results of the layered floors clearly indicate the importance of considering all five impact hammer locations of the tapping machine to achieve a high prediction accuracy, especially at low frequencies. The influence of the impact source and the modal behavior of the floor can lead to high peaks in the radiated sound power level.