ASA - ANSI/ASA S12.18
American National Standard Procedures for Outdoor Measurement of Sound Pressure Level
|Publication Date:||12 May 1994|
This standard describes methods for measuring sound pressure levels in the outdoor environment, taking into account the effects of refraction due to wind and temperature gradients, the effects of atmospheric turbulence, the effects of variable ground impedance, and wind noise.
This standard assumes A-frequency weighting or the use of octave, 1/3-octave, or narrow-band filters, but does not preclude the use of other frequency weighting or other sound descriptors.
This standard prescribes selected meteorological conditions under which sound pressure level measurements shall be made. Certain meteorological conditions are reproducible and correspond to quite stable sound propagation conditions. These optimal conditions yield reproducible measurements and allow the comparison of sound pressure levels measured at different times.
The standard does not prescribe standardized receiver locations. Sound pressure levels may be measured at receiver locations of interest, within certain prescribed limits.
Measurement conditions shall be carefully documented and noted in the report describing the sound pressure level measurements. The measured sound pressure levels shall apply only to the stated conditions and shall not represent the sound pressure levels under other conditions, sites, receiver locations, or sources. In some cases, guidance is provided to adjust the measured sound pressure levels to reference conditions, other sites, or other receiver location.
This standard does not include procedures for measurement of long-term, time-average environmental sound levels in a community for environmental assessment or planning for compatible land uses.
Sound pressure levels measured for determining the sound power radiated by a source are not covered by this standard.
The purpose of this standard is to specify procedures for measuring and reporting sound pressure levels from specifiC sources outdoors and to specify a set of reproducible atmospheric conditions to obtain reproducible measurements.