Effects of the frequency filter type of measurement equipment on evaluation of floor impact sound insulation

This study examines the influence of frequency filters on the evaluation of floor impact sound insulation by comparing the performances of Butterworth and FFT-based filters. Experimental data were collected from 15 residential units with identical floor plans to reflect on-site conditions. The findings reveal that even when the filters comply with IEC 61260-1 Class 1 standards, performance differences exist depending on the type of impact source and evaluation method. For light-weight impact sounds, which are assessed using time-averaging equivalent continuous sound levels, the 12th-order or higher Butterworth filters provided results comparable to those of the FFT-based filter. For heavy-weight impact sounds, which are evaluated using fast time-weighting followed by the maximum sound level, the FFT-based filter showed distinct characteristics, including higher frequency resolution and independence from stabilization time. These features suggest that FFT-based filters may offer advantages in postprocessing over traditional Butterworth filters. This study underscores the importance of understanding filter performance variations in impact sound insulation for regulatory compliance and calls for further investigation of filter selection in practical applications.