The Lawnmowers (Harmonization of Noise Emission Standards) Regulations 1992

11.    METHOD OF CALCULATING THE AVERAGE LEVEL CORRESPONDING TO THE ROOT MEAN SQUARE VALUE OF THE VARIOUS SOUND PRESSURE LEVELS

The root mean square value of the various sound pressure levels resulting either from a series of measurements made at a single point (root mean square in time) or from a series of measurements made at different points on the measuring surface (root mean square in space) can be determined by the following formula:

where:

• L_pAi equals the sound pressure level of the i-th measurement;

• L_pAo is an auxiliary sound pressure level to simplify the calculation (for example, the smallest of the L_pAi values);

• g_i is the auxiliary variable for the i-th measurement:

  

• g_m is the mean value of the g_i variables:

  

The quantity ΔL is defined by:

ΔL = LpAi - LpAo

Table III gives the values of g for different values of ΔL.

Table III

Value of g as a function of ΔL

The table may be extended in either direction.

ΔL dB	g
−20.0	0.010
−19.5	0.011
−19.0	0.013
−18.5	0.014
−18.0	0.016
−17.5	0.018
−17.0	0.020
−16.5	0.022
−16.0	0.025
−15.5	0.028
−15.0	0.032
−14.5	0.035
−14.0	0.040
−13.5	0.045
−13.0	0.050
−12.5	0.056
−12.0	0.063
−11.5	0.071
−11.0	0.079
−10.5	0.089
−10.0	0.100
−9.5	0.112
−9.0	0.126
−8.5	0.141
−8.0	0.158
−7.5	0.178
−7.0	0.2
−6.5	0.224
−6.0	0.251
−5.5	0.282
−5.0	0.316
−4.5	0.355
−4.0	0.398
−3.5	0.447
−3.0	0.501
−2.5	0.562
−2.0	0.631
−1.5	0.708
−1.0	0.794
−0.5	0.891
−0.0	1
0.0	1
0.5	1.12
1.0	1.26
1.5	1.41
2.0	1.58
2.5	1.78
3.0	2.00
3.5	2.24
4.0	2.51
4.5	2.82
5.0	3.16
5.5	3.55
6.0	3.98
6.5	4.47
7.0	5.01
7.5	5.62
8.0	6.31
8.5	7.08
9.0	7.94
9.5	8.91
10.0	10
10.0	10.0
10.5	11.2
11.0	12.6
11.5	14.1
12.0	15.8
12.5	17.8
13.0	20.0
13.5	22.4
14.0	25.1
14.5	28.2
15.0	31.6
15.5	35.5
16.0	39.8
16.5	44.7
17.0	50.1
17.5	56.2
18.0	63.1
18.5	70.8
19.0	79.4
19.5	89.1
20.0	100
20.0	100.0
20.5	112.0
21.0	125.9
21.5	141.3
22.0	158.5
22.5	177.8
23.0	199.5
23.5	223.9
24.0	251.2
24.5	281.8
25.0	316.2
25.5	354.8
26.0	398.1
26.5	446.7
27.0	501.2
27.5	562.3
28.0	631.0
28.5	707.9
29.0	794.3
29.5	891.3
30.0	1000.0