5.—(1) For the purposes of section 49(1) of the Act (approval of measuring devices), subject to paragraph (2), sound level meters which:
(a)comply with the requirements of Class 1 of BS EN 61672; and
(b)are capable of determining the A-weighted sound pressure level using time-weighting ‘F’,
are devices approved for the measurement of the underlying level of noise, when used in accordance with the requirements of regulations 7 and 8.
(2) Where LAN,T measurements are used to determine the underlying level of noise, the devices specified in paragraph (1) must in addition:
(a)sample the sound pressure level at a rate of not less than 10 times per second; and
(b)use in the statistical calculation a class interval of no greater than 0.5 decibels.
(3) When time weighting ‘F’ is used for the purposes of paragraph (1) it shall not exceed 0.6 seconds in a period of no shorter than one minute and no longer than 5 minutes.