Article,
Measurement of low frequency sound in rooms
(2011)
Abstract
Sound pressure levels (SPL) at low frequencies (20 to 200 Hz) are
strongly dependent on measurement position in normal-sized rooms.
The variation of SPL can be above 20 dB between different measurement
locations. However, there is no standardized method to measure such
noise. Firstly, published measurement methods of low frequency noise
were compared. The simplest methods specify only one measurement
point and a 1-h long measurement. This approach does not consider
room modes and it can result in false conclusions. More advanced
methods emphasize the corner positions, which lead to the overestimation
of SPL in respect with occupant's locations. The literature lacks
a simple but occupant-oriented measurement method. The aim of the
study was to develop a simple and reliable method for the measurement
of low frequency noise in all kinds of rooms, like dwellings, industrial
control rooms or patient rooms. The method was developed on the basis
of extensive measurements in 5 rooms. In addition, finite element
modelling FEM was used to supplement the analysis of spatial SPL
variations. The suggested method includes two alternatives for constant
and for intermittent noise. The former is very rapid and it is applied
in the first place. The latter includes also a long-term measurement
which is applied when temporal variations are observed or expected.
In most cases, the constant noise method is sufficient to state whether
the limit values are exceeded or fulfilled. The main attention is
paid to the occupants' locations. The practical application of the
method is demonstrated in one case room. The method should be proposed
to technical committees making new standard proposals.
