scope:

The scope of this standard includes the measurement, with an observer present, of quantities such as equivalent-continuous sound pressure level or sound exposure from a specific source or sources at a specified location. These measurements require several minutes to several hours to perform; they take less than one day to perform. Measurements may be obtained with a standard frequency weighting, may be frequency filtered in a defined manner, or may be frequency filtered by octave band or fractional octave band filters. This standard specifies procedures to effectively eliminate, to the extent possible, the contributions of extraneous background sound from the source-specific measurements. Measurement procedures in this standard require the presence of an instrument operator and are not applicable to measurements by unattended instruments. This standard does not define specific measures or limits for environmental sounds or recommend measurement locations or durations.

The purposes of this standard are to (a) specify procedures for measurement of environmental sound from a specific source or sources at a specified location, and (b) to specify procedures to effectively eliminate the contributions of extraneous background sounds from the source-specific measurements. Sound pressure levels are measured with an observer present to record the data described in this part.

This standard is applicable to the measurement of quantities such as equivalent-continuous sound pressure level or sound exposure level from a specific source or sources with an observer present. Major applications of this Standard include:

1. Assessment of environmental sound

2. Measurement of source emissions as equivalent-continuous sound pressure level (LEQ), or as sound exposure level (SEL)

3. Measurement of received sound as LEQ

4. Correction of LEQ measurements for the background sound

NOTE Source emissions typically are measured only when the direct measurement of the received sound is not practical or when the source is not yet in operation. In either case, the received sound must be predicted using the measured source emissions. Annex A contains an informative discussion regarding source emissions and received sound, and clause 7.4 discusses, in general terms, moving closer to the source when the source cannot be turned off, and, as a result of not being able to be turned off, correction for the background is problematic.