In rare cases, where the low frequency noise is obvious and constant it will be
possible to carry out an assessment on the spot.
In most cases a period of unattended monitoring will be required. If possible,
recordings should be made continuously for a minimum of three days since the
complainant’s response can be affected by the presence of the equipment and is often
untypical immediately after it is installed. If data storage capacity is limited then
choose a period when the noise is typically at its most disturbing (usually this is night
time). Recordings made during the night are usually considerably easier to analyse.
This is because there is minimum interference from other sources. For example,
movements within the building always produce elevated levels of low frequency noise
that can be difficult to distinguish from ‘true’ low frequency noise. Therefore, night
time recordings are preferred. However, the overriding consideration is that the
recordings are made at a time when the complainant says the sound is present.