Møller, Henrik

Olesen, Søren Krarup

Pedersen, Steffen

Persson-Waye, Kerstin

Due to standing waves, the sound pressure level within a room may vary as much as 20-30 dB with low-frequency tonal noise, somewhat less with noise bands. For assessment of annoyance from low-frequency noise it is relevant to measure a level close to the highest level of the room, rather than a room average. As a means in this, current Swedish and Danish measurement methods include corner measurements. These positions are however still with some specified height and distance to the walls, and they may not effectively serve the purpose. Alternative measurement positions were investigated based on theoretical considerations and observations from numerical simulations. The performance of the methods in practice was studied by measurements in three rooms, while various low-frequency sounds were produced in adjacent rooms. The sound pressure level was measured in 1) the entire room by scanning, 2) corner positions specified by Swedish and Danish measurement methods, and 3) all three-dimensional corners. The level that is exceeded in 10% of the space in a room (L90%) was found to be a reasonable target for a measurement method rather than the absolute maximum. Good results can be expected with the Swedish method, as the Swedish corner position is obtained by scanning and yields levels close to the target; however there are serious concerns regarding the use of C-weighting in the scanning. With the Danish method, good results can only be expected, if complainants can accurately appoint measurement positions, since the corner position in this method generally fails to represent the high levels in the room. As an alternative method, it is proposed to use the power average of measurements in some or all three-dimensional corners. This method is simple and seems to offer reliable and repeatable results in all rooms and at all frequencies

Indoor measurements of sound at low frequencies

http://vbn.aau.dk/files/227978109/2006_Pedersen_et_al_LFN_Bristol.pdf

Indoor measurements of sound at low frequencies

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