TNAG-1613-FCO40-2221-Executive-Council-of-Hong-Kong-memoranda-and-minutes-of-meet-1987 — Page 256

ANNEX GENERAL CALIBRATION AND MEASUREMENT PROCEDURES

1.

Instrumentation

For the purpose of this Technical Memorandum sound level meters shall

comply with International Electrotechnical

Commission

Publications

651: 1980 (Type 1), and 804 : 1985 (Type 1), and other noise measuring and analysis instrumentation shall be of a comparable professional

acoustical principles and practices shall be

of the noise under

quality.

Standard

followed in the

measurement

investigation.

and analysis

2. Calibration Procedures

2.1

Overall Calibration

To ensure measurement accuracy, within 12 months immediately prior to taking any noise measurement or undertaking any noise analysis for the

this Technical Memorandum, purpose of

overall calibration of the

instrumentation involved shall have been carried out in a laboratory

suitably equipped for the purpose.

2.2 Field Calibration

.?

known

sound

level

at

known a

Immediately prior to and following each noise measurement the accuracy of the sound level meter shall be checked using an acoustic calibrator

generating

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.

pressure

Where a tape recorder forms an integral part of the measuring system, a constant calibration signal corresponding to a known sound pressure level at a known frequency shall be applied at the beginning and end of each noise recording. A tape recording may be accepted as valid only if at the time of subsequent laboratory analysis the calibration levels from before and after the noise recording agree to within 1.0 dB.