Field measurement of airborne sound insulation between rooms with non-diffuse sound fields at low frequencies

Revision of international standards on field measurements of airborne, impact and facade sound insulation to form the ISO 16283 series

“…In addition it was noted that problems with poor repeatability and reproducibility become most apparent with room volumes below 25 m 3 where the 50, 63 and 80 Hz bands only have a single mode that falls within the filter bandwidth as indicated in the room mode calculations in Ref. [7]. The implication of defining the lowfrequency procedure in ISO 16283 for use with room volumes below 25 m 3 is that in most countries it will be used for bedrooms significantly more often than living rooms.…”

“…Hence during the writing of ISO 16283 it was necessary to identify a maximum room volume to which the low-frequency measurement procedure would be applied. Hopkins and Turner [7] initially designed this procedure for room volumes below 50 m 3 because ISO 140 Part 4 Annex D contained guidance on measurements at low frequencies which stated that ''In lowfrequency bands (lower than about 400 Hz in general and especially lower than 100 Hz), no diffuse-field conditions in the test rooms can be expected especially when room volumes of only 50 m 3 or even less are considered'' and that ''In rooms with small volumes and unfavourable dimensions, it is not always possible to obtain reliable results of low-frequency measurements. At least one room dimension should be of one wavelength (sic) and another of at least half a wavelength of the lowest band centre frequency, and there should be the space to position the source and the microphones according to the requirements''.…”

“…This was based on an approach proposed in a paper by Hopkins and Turner [7] which adapted and extended an approach for the measurement of low-frequency noise from technical installations by Simmons [23]. The procedure essentially augments the ISO 140 field measurement procedures with additional sound pressure level and reverberation time measurements that are described in this section.…”

“…The aim of the low-frequency measurement procedure is to estimate the room average sound pressure level which is defined as the energy average level that is calculated using all possible microphone positions in a room [7]. This average level includes all the possible microphone positions near the walls/floors and the corners.…”

“…A specific technical problem for airborne, impact and facade sound insulation concerned the fact that the ISO 140 measurement procedures were prone to poor repeatability and reproducibility at low frequencies [7]. The uncertainty was quantified in ISO 12999 Part 1 [8] and in more recent work [e.g.…”