BS EN ISO 3744-2010 pdf download.Acoustics – Determination of sound power levels and sound energy levels of noise sources using sound pressure 一Engineering methods for an essentially free field over a reflecting plane (ISO 3744:2010).
4 Test environment
4.1 General
The test environments that are applicable ior measurements in accoraance witn Ems International sianoara
are:
a) a laboratory room or a flat outdoor area which is adequately isolated from background noise (see 4.2) and which provides an acoustic free field over a reflecting plane:
b) a room or a flat outdoor area which is adequately isolated from background noise (see 4,2) and in which an environmental correction can be applied to allow for a limited contribution from the reverberant field to the sound pressures on the measurement surface.
Environmental conditions having an adverse effect on the microphones used for the measurements (e.g. strong electric or magnetic fields, wind, impingement of air discharge from the noise source being tested, high or low temperatures) shall be avoided. The instructions of the manufacturer of the measuring instrumentation regarding adverse environmental conditions shall be followed.
In an outdoor area, care shall be taken to minimize the effects of adverse meteorological conditions (e.g. temperature, humidity, wind, precipitation) on the sound propagation and on sound generation over the frequency range of interest or on the background noise during the course of the measurements.
When a reflecting surface is not a ground plane or is not an integral part of a test room surface, particular care should be exercised to ensure that the plane does not radiate any appreciable sound due to vibrations.
4.2 Criteria for background noise
4.2.1 Relative criteria
4.2.1.1 General
The time-averaged sound pressure level of the background noise measured and averaged (see 8.2.2) over the microphone positions, or traverses, on the measurement surface, shall be at least 6 dB, and preferably more than 15 dB, below the corresponding uncorrected time-averaged sound pressure level of the noise source under test when measured in the presence of this background noise. For measurements in frequency bands, this requirement shall be met in each frequency band within the frequency range of interest.
If this requirement is met, the background noise criteria of this International Standard are satisfied.
NOTE 1 A similar criterion Is applied to single event sound pressure levels: the measurement time interval for the time average is the same as the measurement time interval associated with the single event.
NOTE 2 The noise associated with the microphone traversing mechanism, if one is used foi’ the measurements, is considered to be part of the background noise. In such cases, the background noise is measured with the traversing mechanism operating.BS EN ISO 3744 pdf download.