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.