An Investigation of Floor Impact Sources and Perception Models of Impact Sounds

Abstract

The present work compared the physical and psychoacoustical characteristics of standard impact sources with those of human impacts, and proposed the perception models of annoyance for impact sounds with respect to temporal and spatial aspects. Impact ball (heavy/soft impact source) was selected as an appropriate standard floor impact source simulating real floor impacts based on the objective evaluation, which includes mechanical impedance, impact force, impact sound pressure level measurement, and similarity judgment. Using the empirical relationships between standard floor impact sources, two methodologies for converting the levels produced by bang machine and tapping machine into those of impact ball were suggested; one is based on the level differences between impact sources and the other on the basis of regression analysis. Then, measurements using impact ball were conducted in a variety of apartment buildings with different floor structure and coverings. Variations in frequency characteristics were found in the measurement results, thus these were classified into three groups, Groups A-C. Differences between Groups A-C were clarified using SQ (sound quality) metrics. The present work suggested LAmax as a practical descriptor of impact ball sounds since it showed good correlation with annoyance and the measurement and the calculation procedure is much simpler than other metrics. Finally, perception models of impact ball sounds were developed in relation to temporal aspects and spatial characteristics, respectively. When the spatial characteristics kept constant, perceptions of annoyance for impact ball sounds were affected mainly by the differences in pitch (fluctuation strength) as well as loudness. Another perception model comprised of IACC (Interaural cross- correlation function) was also proposed through auditory experiments. It was found that IACC had an effect on the perception of impact ball sounds with sound pressure level (SPL), and the contribution of IACC on perception of impact ball sounds was around 20%. The present work may contribute to a better understanding of the floor impact sources and human perception of annoyance for impact ball sounds.