4.1 Situations for which outdoor sound level data are required include, but are not limited to, comparison of sound levels with criteria or regulatory limits.

4.2 This guide provides information to (1) measure outdoor sound level in the vicinity of outdoor fixed noise sources, and (2) document other observations necessary for the measurements. This guide provides a standard procedure for a trained acoustical professional that will produce results and documentation which are consistent with the purposes cited in 1.1.1 – 1.1.5.

4.3 These sound measurements should be performed by or under the direction of a person experienced in the measurement and analysis of outdoor sound, and who is familiar with the use of the required equipment and techniques.

4.4 This guide can be used by individuals, regulatory agencies, or others as a measurement guide to collect data on the sound level received from a fixed source within the constraints cited in Section 8 and Appendix X1 and Appendix X2.

4.5 This guide can be used to establish compliance or noncompliance at the time, distance, and conditions during which the data were obtained. However, this guide is only a measurement procedure and does not address the problem of projecting the acquired data outside those conditions, other times of day, other distances, or comparison with specific criteria. In particular, for a given sound source level, distant noise levels will often be found to be greater at night than during the day.

1.1 This guide covers the measurement of outdoor sound due to a fixed sound source such as a siren, stationary pump, power plant, or music amphitheater. Procedures characterize the location, sound level, spectral content, and temporal characteristics of that sound source at the time of measurement. Users should be aware that wind and temperature gradients can cause significant variations in sound levels beyond 300 m. With appropriate caution, the use of measurements resulting from this guide include but are not limited to:

1.1.1 Assessing compliance with applicable regulations,

1.1.2 Monitoring the effectiveness of a noise reduction plan,

1.1.3 Verifying the effectiveness of measures for mitigation of noise impact,

1.1.4 Validating sound prediction models, and

1.1.5 Obtaining source data for use in sound prediction models.

1.2 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of regulatory limitations prior to use.

1.3 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.