ANNEX - GENERAL CALIBRATION AND MEASUREMENT PROCEDURES
-
Instrumentation
For the purpose of this Technical Memorandum sound level meters shall comply with International Electrotechnical Commission Publications 651:1979 (Type 1) and 804:1985 (Type 1), and other noise measuring and analysis instrumentation shall be of a comparable professional quality. Standard acoustical principles and practices shall be followed in the measurement and analysis of the noise under investigation.
-
Calibration Procedures
Immediately prior to and following each noise measurement the accuracy of the sound level meter shall be checked using an acoustic calibrator generating a known sound pressure level at a known frequency. Measurements may be accepted as valid only if the calibration levels from before and after the noise measurement agree to within 1.0 dB.
-
Measurement Procedures
3.1 Assessment Point
Noise levels shall be determined by carrying out measurements at the assessment point. Where a measurement is to be carried out at a building, the assessment point shall normally be at a position 1 m from the exterior of the building facade but may be at any other point considered to be appropriate by the Authority. Where a measurement is to be made of noise being received at a place other than a building, the assessment point shall be at a position 1.2 m above the ground, at a particular point considered appropriate by the Authority.3.2 Noise Units and Descriptors
Any noise measurement shall be made in terms of the A-weighted equivalent continuous sound pressure level (Leq) measured with an integrating sound level meter. Such measurement shall be made over any 5-minute period during the CNP period under consideration.3.3 Rounding of Noise Levels
All noise measurements shall be rounded to the nearest whole dB(A), with values of 0.5 or more being rounded upwards.3.4 Weather Conditions
Noise measurements should be made in accordance with standard acoustical principles and practices in relation to weather conditions.
