Effect of reinforced concrete structure type on low frequency heavy impact sound in residential buildings

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This study experimentally investigated the effect of reinforced concrete structure type on the propagation of low-frequency heavy impact sounds below 100 Hz in apartment units. Field measurements were conducted for two floor plans each in wall-slab and wall-slab with columns structure types. Measurements were made repeatedly in four identical units for each floor plan at different stories to minimize inherent variations in field measurements. A bang machine was used to produce an impact sound in the center and corner of the largest room in the unit. Slab and wall accelerations were recorded, as was the sound level, in the unit below the bang machine to verify the relationship between structural dynamic properties and the heavy impact sound level. Test results indicate that the differences in impact sound level between the two structure types were negligible in the case of center-of-room excitation. On the other hand, in the case of corner-of-room excitation, units in wall-slab with columns buildings generated significantly greater impact sound level than units in wall-slab buildings particularly at the structural mode frequencies. This result can be attributed to the inability of the lightweight nonstructural walls in the wall-slab with columns buildings to restrain the vibration of the slab corner. Accordingly, lightweight nonstructural walls significantly increased the slab acceleration in the case of corner-of-room excitation. To verify this observation, the slab constraint conditions at the boundaries imposed by the concrete walls or lightweight nonstructural walls observed in the field tests were validated by finite element analysis.