ALTERNATIVE METHOD FOR LOW FREQUENCY IMPACT SOUND MEASUREMENT FOR BUILDING FIELD TESTS

Abstract

What do high heels, dog nails, and dragging furniture have in common? They are all frequent sources of noise pollution and annoyance in multi-story buildings. Building codes exist to control and mitigate such noise, but these codes are outdated and fail to protect the residents against noise annoyance. Footstep noise is still the number one cause of complaints among the residents. The impact performance of floor-ceiling assemblies is characterized using a single-number rating called the Impact Sound Rating (ISR). A standard tapping machine is used in pre-defined locations on the floor and the radiated Sound Pressure Level (SPL) is measured in the receiving room downstairs to calculate the ISR rating. This measurement method has a lot of variabilities that cause problems for the residents or the acoustical consultants. The force from the tapping machine depends on the floor compliance but it is not measured for the test. An FRF-like measurement is required to account for this force difference and compare the performance of different assemblies. Additionally, a non-diffuse sound field exists in rooms at low frequencies that cause high variation in the test results based on the microphone positions. In this work, a new measurement method is proposed that provides an FRF-like (without consideration of phase) performance using a ratio of autopower spectra (RPF) and shows an improved reproducibility in the low-frequency non-diffuse sound field region. A 1 – 1.5 dB measurement variability is expected as compared to 4 – 10 dB variability observed with the existing method. The guidelines to conduct the proposed test are detailed in this work.