Influence of birdsong intervention on annoyance due to residential noise in multi-family housing buildings: Dependency of spectral characteristics

This study investigated the reduction in annoyance from residential noise sources in multi-family housing buildings from intervened birdsongs, which addressed the lack of research on sound masking in residential spaces and the use of birdsongs as maskers for diverse residential noise sources. Based on frequency and temporal characteristics, seven residential noise sources (child jumping, child running, conversation, outdoor unit of air conditioner, piledriver, plumbing, and traffic noise) were chosen using clustering methods, and two birdsongs were selected for this study. The laboratory experiment consisted of two sessions: single residential noise sources and combined sounds (residential noise and birdsong). The participants evaluated the degree of annoyance using a 7-point Korean verbal scale. When birdsongs were added to residential noise, annoyance reduction was observed for most sound sources. Among these, children jumping and running showed the most significant reduction in annoyance. Analysis of the differences in physical parameters between the combined sounds and single residential noise sources revealed that frequency characteristics (Δf_{octave at max}) were significantly correlated with annoyance. This suggests that when birdsongs are audible owing to different dominant frequency ranges from residential noise, attention from added birdsongs yields informational masking, thus reducing annoyance. The results of this study can provide basic data for the design of sound-masking systems in residential spaces.