Cause and perception of amplitude modulation of heavy-weight impact sounds in concrete wall structures

Abstract

This study investigated amplitude-modulation effects on the heavy-weight floor impact sound caused by a vibration of concrete wall construction. The fundamental resonance of a floor in concrete wall construction consists of two closely spaced vibration modes. These modes were identified from experimental modal analysis of an actual multi-story building. The modes corresponded to in-phase and out-of-phase vibrations of the upper and lower floors. The rigidity of the side walls had influence on the difference between the natural frequencies of the two modes. Low-frequency modulated sounds were generated in a room by the simultaneous excitations of the two vibration modes. The heavy-weight impact sounds were analyzed using auditory experiments to determine the amplitude-modulation effects on the perceived annoyance. The highly modulated impact sounds were judged to be 3-5 dB more annoying than the one having the same level without modulation. Consequently, impact sound transmission from floors connected by less rigid side walls exhibited lower annoyance.