Variations in impact sound level as a function of tapping machine position

Abstract

Impact insulation class testing per ASTM E 492 requires measurement of the sound field at exactly four tapping machine positions. Previous research by the authors [J. Acoust. Soc. Am. 121, 3113 (2007), J. Acoust. Soc. Am. 122, 2955 (2007)] indicated that for field tests, the variation between tapping machine positions was small. To our knowledge, a systematic investigation has not been performed for tapping machine positions in the laboratory, and some recent results indicate that the variation may be larger than expected. Large variation in sound level may be inherent to the method, or may point to problems in construction or installation of flooring materials. The variations with tapping machine position are analyzed for a set of laboratory tests, and the previous field test studies are updated with additional data. The authors investigate possible changes to the standards to mandate a maximum allowable variation between tapping machine positions, and to require additional positions as necessary.

Measurement of low frequency impact insulation

“…Using the ASTM standard tapping machine positions, two of the positions are directly above a joist and two are between the joists. The previous studies [9], [10] did not identify any systematic differences between the tapping machine positions. However, those studies did not examine the bands below 100 Hz, while Larsson et al observed this effect only below 100 Hz.…”

“…The authors have presented two studies [9], [10] on the effect of tapping machine position. These studies focused on the effects of number of tapping machine positions that are averaged.…”