Reduction of heavy-weight impact sounds with sound absorbers for renovation ( 04.07) of a box-type building with 120 mm-thick concrete slab

In this study, effects of low frequency sound absorbers on reduction of heavy-weight impact noise were investigated in a box-type test building to improve sound isolation performances against impact noises. Two types of sound absorbers were prepared: frame type plane absorber using wood wool boards and corner bass trap using PU foam. Sound absorption properties of the absorbers were measured in a reverberation chamber in accordance with ISO 354. Then, the absorbers were installed in a box-type test building with concrete slab of 120 mm. Bang machine was employed as a heavy-weight sound source. In receiving room, maximum levels were measured at 54 points spacing by width 500 mm and length 600 mm. The experiment consists of 6 cases according to combination of the installed sound absorbers. As results, the case adding bass trap on top and side corners of receiving room showed maximum 3 dB reductions in terms of single number quantity based on KS F 2810-2 and KS F 2863-2. These sound absorbers were helpful to reduce room modes at 50 to 63 Hz. In addition, practical design approach of sound absorbers was discussed for further study.