1.1 General
This International Standard specifies methods for determining the sound power level or sound energy level of a noise source from sound pressure levels measured in a reverberation test room. The sound power level (or, in the case of noise bursts or transient noise emission, the sound energy level) produced by the noise source, in frequency bands of width one-third-octave, is calculated using those measurements, including corrections to allow for any differences between the meteorological conditions at the time and place of the test and those corresponding to a reference characteristic impedance. Measurement and calculation procedures are given for both a direct method and a comparison method of determining the sound power level and the sound energy level.
In general, the frequency range of interest includes the one-third-octave bands with mid-band frequencies from 100Hz to 10000Hz. Guidelines for the application of the specified methods over an extended frequency range in respect to lower frequencies are given in AnnexE. This International Standard is not applicable to frequency ranges above the 10000Hz one-third-octave band.
NOTE For higher frequencies, the methods specified in ISO9295 can be used.
1.2 Types of noise and noise sources
The methods specified in this International Standard are suitable for all types of noise (steady, non-steady, fluctuating, isolated bursts of sound energy, etc.) defined in ISO12001.
The noise source under test can be a device, machine, component or sub-assembly. This International Standard is applicable to noise sources with a volume not greater than 2%of the volume of the reverberation test room. For a source with a volume greater than 2%of the volume of the test room, it is possible that the achievement of results as defined in ISO12001:1996, accuracy grade1 (precision grade) is not feasible.
NOTE In specific cases, the source volume can be increased to a maximum of 5%of the room volume. In such cases, the relevant noise test code indicates the possible consequences on the measurement uncertainty.
1.3 Reverberation test room
The test rooms that are applicable for measurements made in accordance with this International Standard are reverberation test rooms meeting specified requirements (see Clause5).
1.4Measurement uncertainty
Information is given on the uncertainty of the sound power levels and sound energy levels determined in accordance with this International Standard, for measurements made in specific frequency bands and for the A-weighted sum of all frequency bands. The uncertainty conforms to ISO12001:1996, accuracy grade1 (precision grade).