Measurement of Transmission Functions in Lightweight Buildings for the Prediction of Structure-Borne Sound Transmission From Machinery

Abstract

This paper develops and assesses protocols for the 2 measurement of transmission functions in lightweight 3 buildings. A transmission function is defined that 4 relates the spatial-average sound pressure level in a 5 room to the structure-borne sound power injected into 6 a wall or floor. The intention is to facilitate the pre-7 diction of structure-borne sound transmission from 8 machinery to receiving rooms. Errors in the mea-9 surement of the power input can be reduced by using 10 a pair of accelerometers on either side of the excita-11 tion point rather than a single accelerometer on one 12 side. Laboratory measurements on a timber-frame 13 wall indicate that steady-state excitation using an 14 electrodynamic shaker and transient excitation with a 15 force hammer can be considered as equivalent. Mea-16 sured transmission functions from a laboratory test 17 construction below 500 Hz are found not to be signifi-18 cantly affected by the choice of excitation position be-19 ing directly above a stud or in a bay. Laboratory and 20 field results on different timber-frame walls indicate 21 that with transient excitation using a force hammer, 22 the transmission function is measurable in vertically-, 23 horizontally-and diagonally-adjacent receiving rooms 24 over the frequency range from 20 to 1 k Hz. The ap-25 proach has been applied in field measurements which 26 indicate that there is potential to create databases of 27 average transmission functions as a simplified predic-28 tion tool for sound pressure levels from service equip-29 ment in buildings.

Experimental investigation of the low-frequency impact sound transfer function of lightweight wooden floors via heel drops

“…On lightweight floor structures, a significant difference can be found in the driving-point mobility between the measurements at joist and inter-joist positions [11,18]. This is also observed in the current work, as shown in Figure 10a, affecting only the LWF but hardly the LWF + CFF (see the impact positions in Fig.…”

“…3). On the other hand, this discrepancy between the joist and inter-joist excitation is less pronounced in the transfer mobility and impact sound transfer function as shown in Figures 10 and 11 (a similar result was observed by [11]). For these two parameters, obvious deviations are only observed from 160 Hz onward.…”

“…This provides a way to compare the performances of various floors, but it does not intuitively reflect the ability of a structure to radiate sound as the force level is included in this value [1,6]. In comparison, the transfer function allows a evaluation on the behavior of a floor-room system, and provides a convenient way to investigate the sensitivity of the floor-room system to generate noise at low frequencies [9,11].…”

“…The conventional impact sources for floor modal testing, e.g., impact hammer and shaker, have been applied in the measurement of structure-borne sound in buildings [11]. The latter assures high-quality modal tests, while the former allows convenient in-situ floor structure measurements [12].…”

“…The latter assures high-quality modal tests, while the former allows convenient in-situ floor structure measurements [12]. However, the sound generated by these sources tends to have a low signal-to-noise ratio in the low-frequency range [11]. Moreover, they cannot provide an acoustical scenario close to those given by the human activities [2,13], as the floor responds differently due to its interaction with humans.…”