Downstairs resident classification characteristics for upstairs walking vibration noise in an apartment building under virtual reality environment

Psychoacoustic experiments were performed to investigate head-related transfer function (HRTF) and head- mounted display (HMD) effects, to develop a new virtual-reality (VR)-based noise assessment methodology and classification method for heavy-weight impact sounds in an apartment indoor environment. Sound pressure levels and frequency characteristics before and after HRTF application were examined to reproduce the upstairs condition (overhead movement), for a heavy-weight impact source recorded in an apartment living room. Floor impact noise was assessed using the HMD by modeling a typical living room. For four environments (NONE, HRTF, HMD, and HRTF + HMD), subjective responses (annoyance, allowance limit, semantic expression) were examined for 38-62-dB maximum sound pressure levels with an A-weighted frequency response and fast time constant. Directional information through the HRTF significantly increased annoyance and decreased the allowance limit, and HMD visual information partially (1.2 times) affected the allowance limit in a high inter-floor noise environment owing to increased visual involvement (56 dBA). The semantic expression assessment revealed comprehensive inter-floor noise responses of dissatisfaction, irregularity, and discontinuity, and confirmed greater annoyance due to walking vibration noise in an environment with directional information, because of increased perception of heavy-impact sound-induced discomfort. Regarding annoyance- and allowance-limit- based classification, the satisfaction standards for low-noise environments were assessed as 6-7 dB lower than those of previous studies when both HRTF and HMD were applied, confirming that test subjects respond to noise more sensitively in a virtual environment where audiovisual information is provided. Therefore, a new indoor noise assessment methodology for environmental factors is proposed herein.