METHOD FOR NOISE MEASUREMENT
The noise level at a pit or quarry shall be measured according to the following formula:
| LI+5 Lx |
| ______ ____ |
B = S + I - A + 10 log10 | (.0014m) 10 10 + 10 10 |
S = 5 where there are one or several importunate frequency bands;
S = 0 where there is no importunate frequency band;
I = 5 where there is one or several information bearing noises;
I = 0 where there is no information bearing noise;
A = A1 + (A2 - A3) calculated as follows:
A1 = attenuation caused by distance
A1 = 20 log10 ___
d1 = distance from the pit or quarry to the point of measurement
d2 = distance from the pit or quarry and the evaluation point
A2 = attenuation at the evaluation point caused by a barrier
A3 = attenuation at the measuring point caused by the same barrier
LI = equivalent level of impact noise:
Calculation of the arithmetic mean of the maximum energies, during the period of emission of the impact noises produced during the sampling time period which are recorded at the point of measurement.
The formula to be used is as follows:
dBn = maximum noise of the nth impact noise during its emission period
m = total number of impacts during the emission period.
If the number of impacts is over 720/h, m = 720.
Lx = equivalent level of a noise:
Equivalent level of a noise at the point of measurement during its period of emission during a sampling period.
The formula to be used is the following:
where fi = time interval (expressed in a percentage of the sampling time) during which the noise level is less than the limit of class i.
Where the pit or quarry is not in a period of emission, the corresponding fi shall be equal to 0.
Li = sound level in dBA corresponding to the average of class i.
The scope of class I must be fixed at a value equal or less than 2 2BA and the period of sampling must be equal or less than 0.1 seconds.
For the purposes of this measurement method, the normal sampling time shall be 60 consecutive minutes. If the sampling lasts longer than 60 minutes, an adjustment must be made so that the ratio between the periods of emission and the pause is the same.
All the measurements shall be made in dBA using the rapid response of the sound level meter. The sound level meter and the octave band filters must comply with the standards in publications 179 (2nd edition, 1973) and 225 (1st edition, 1966) of the Central Office of the International Electrotechnical Commission.