Technical Memorandum for the Assessment of Noise from Places Other Than Domestic Premises, Public Places or Construction Sites

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. Where the noise under investigation is transmitted to the NSR primarily either through the structural elements of the building; through openings other than those at the facade of the building; or through specially provided glazing at the facade of the building as considers appropriate for reducing the noise, the assessment point shall be at a particular internal location which the Authority considers appropriate having regard to the normal occupancy of the building.

3.2	Noise Units and Descriptors Any noise measurement to determine the MNL 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 30 minute period or any shorter period when the Authority is satisfied that the noise under investigation is essentially steady over a 30 minute period, which shall be taken to be the STP.

3.3	Rounding of Noise Levels With the exception of the CNL which should be calculated to the nearest whole dB(A), with values of 0.5 or more being rounded upwards, other measured or calculated noise levels shall be determined to the nearest 0.1 dB(A) or dB, with values of 0.05 or more being rounded upwards.

3.4	Weather Conditions Noise measurements should be made in accordance with international acoustical standards and practices in relation to weather conditions.