ANSI / ASA S12.51 / ISO 3741
Standard: ANSI / ASA S12.51 / ISO 3741: Acoustics – Determination of sound power levels and sound energy levels of noise sources using sound pressure – Precision methods for reverberation test rooms
Certification Required: Acoustical certification is currently not required by building codes, but sound power level ratings might be required for certain devices, machines, components or sub-assemblies in order for them to be accepted by certain countries or industries.
Scope: This test method covers the laboratory measurement of sound pressure levels of noise sources in a reverberation chamber. The sound pressure level data is used to calculate the sound power level and A-weighted sound power level of the tested device.
Applicable Products: Washer and dryers, dishwashers, refrigerators, power tools, vacuum cleaners, office equipment and many other types of products.
Test Procedure: The noise source to be tested shall be installed in the reverberation test room at one or more locations relative to the boundary surfaces, as if it were in normal use. Base-mounted machinery and equipment intended exclusively for mounting in front of a wall shall be installed on an acoustically hard floor surface in front of an acoustically hard wall. Wall-mounted machinery and equipment shall be placed on an acoustically hard wall. The sound power or sound energy emitted by a source can be affected by the load applied, the running speed, and the conditions under which it is operating. The source shall be tested, wherever possible, under conditions that are reproducible and representative of the noisiest operation in typical usage. The load, speed and operating conditions shall either be held constant during the test, or varied through a defined cycle in a controlled manner. The direct method is used to measure the sound pressure levels, background noise levels and room sound absorption at five different microphone positions.
End Result: The test report will include the sound pressure levels, sound power levels and A-weighted sound power levels from 80 to 10,000 Hertz, and as well as the overall A-weighted sound power level.
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