AS 1055:2018 Australian Standard Acoustics—Description and measurement of environmental noise
8.2.1 General
The noise shall be measured at the relevant time and place (see Note 4). Where the chosen descriptors are the adjusted percent exceedance A-weighted sound pressure level (L A%,adj,T ) and the background sound pressure level (L A90,T ), the measurements shall be made in accordance with Clause 8.2.2. Where the chosen descriptor is the rating sound level (L Ar,T ), the measurements shall be made in accordance with Clause 8.2.4. Where the descriptor is the percent exceedance A-weighted sound pressure level (L A%,T ), the measurement shall be made in accordance with Clause 8.2.5.
NOTES: 1 Where appropriate, the ambient sound, with and without the noise investigated, should be recorded using instrumentation such that the whole measurement system has an accuracy at least conforming to the requirements of Class 2 of AS IEC 61672.1 for subsequent analysis.
2 Additionally, other types of measurement may be desirable depending on the situation to be investigated, or may be specified by the relevant regulatory authority. Such measurements may include spectrum analysis of the ambient sound, with and without the noise being investigated (octave band, one-third octave band, or narrow-band analysis, as necessary), where the noise has characteristics such as narrow-band components or low-frequency components not adequately reflected in the A-weighted level.
3 Any unusual noise (e.g. dogs barking or insects and the like) not relevant to the measurement of the parameter being reported should be excluded from the data, or if this is not possible, its presence should be noted and recorded.
4 If measurements are performed at other than the relevant time and place, justification should be provided. Relevant time implies at the same time of day in similar conditions and similar locations.
5 If it is not possible to measure the background L A90,T at the relevant place and time in the absence of the noise that is being investigated, it should be measured at a similar location. This requirement may arise because a source operates continuously 24 h per day 7 days per week and an alternative location is required where the subject source is not contributing but other non-subject sources are similar. A similar location is one which would be expected to have a similar background level to the site under consideration (for example, by reason of traffic flow or general industrial activity and includes similar distances from other non- subject sources and times of measurement. Sometimes this may be difficult to achieve).