Comparison of energy and spatial properties between direct and flanking heavy-weight floor impact sound in apartment buildings with bearing wall

In apartments with a bearing wall system, floor impact sound is transmitted through load-bearing walls to multiple floors, and it could lead to complaints because of misidentification of the source floor. For the correct identification of the floor from where low-frequency floor impact sounds originate, the characteristics of sound transmitted to the different floors should be determined. In bearing-wall-system apartments, floor impact sounds can be classified into directly transmitted floor impact sounds, which are transmitted through the floor slab to the floor directly below, and flanking transmitted floor impact sounds, which are transmitted through walls to distant floors. It is challenging to differentiate between the two transmission types solely on the basis of the fundamental sound energy characteristics such as frequency spectrum distribution and attenuation. In this study, binaural recordings were conducted on a floor for rubber ball impact sounds generated from multiple floors in apartment buildings, and differences between directly transmitted and flanking transmitted impact sounds were examined by comparing the frequency spectra, early sound energy ratios, and interaural cross-correlation coefficient (IACC). In particular, directly transmitted impact sounds from the upper floor were found to exhibit higher early sound energy ratios and higher IACC values than flanking transmitted impact sounds. In cases of residential noise complaints, these two parameters can potentially help determine whether the floor impact noise originated from the upper floor.