Acoustics-Measurement of Airborne Noise Emitted By Construction Equipment Intended for Outdoor Use-Method for Determining Compliance With Noise Limits
This SAE Standard describes a method for measuring the weighted sound pressure levels at prescribed microphone positions in the proximity of a device or machine for outdoor use, in order to determine compliance with noise limits. The A-weighted sound power level of the source is calculated from the measured values.
1. When nine or more microphone positions are prescribed in the proximity of the source (as in Section 7), the A-weighted sound power levels determined in accordance with this document tend to result in standard deviations less than approximately 2 dB, provided that the spectrum does not contain pronounced discrete frequencies; if it does, the magnitude of the uncertainties will be larger and no general rules for the magnitude of the uncertainties can be given. These standard deviations reflect the cumulative effects of all causes of measurement uncertainty, excluding variations in the sound power level from machine to machine or from test to test, which may be caused, for example, by changes in the mounting or operating conditions of the source.
2. For measurements made using a hemispherical measurement suface, the directivity index of the source may be calculated according to the description of appendix B.
3. Measurement of A-weighted sound pressure levels at the operator's postion(s) is not described in this document.
4. The results of noise measurements made according to this document are obtained under prescribed conditions and iwll not necessarily correspond to the noise experienced from the equipment when it is in operation on a construction site.