Unlock the myth of low-frequency footstep thumping noise in lightweight wood floors

Abstract

Major occupants' complaints received in lightweight wood floors of Impact Insulation Class (IIC) above 55, are low-frequency footstep thumping noise. Lack of understanding of fundamentals and solutions motived this study. A series experiments were conducted to answer the following questions: 1) what are the frequency range of the low-frequency footstep thumping noises heard by the occupants in mass timber slab floor and in light frame wood joisted floor when the floors are impacted by the ISO tapping machine, footsteps of a person walking with shoes, and with bare foot? 2) how look like the impact sound spectrums below 50 Hz (ISO) or below 100 Hz (ASTM)? 3) Can the tapping machine excite the low-frequency noise down to the range of wood floor natural frequency around 15 Hz? 3) Can the current measurement system measure the sound signals at such low frequency range reliably? 4) can the measured spectrums of impact sound signals reveal the low-frequency impact noise issues? 5) what are the special construction details of the wood floors contributing to the low-frequency impact noise problem? 6) what are the solutions for the problem? Our experiments answered the questions. The findings and solutions will be shared in the full-length paper.