Extract from Annex 1 of Planning Policy Guidance Note 24: Planning and Noise (September 1994)
| NOISE LEVELS° CORRESPONDING TO THE NOISE EXPOSURE CATEGORIES FOR NEW DWELLINGS LAeq,T dB |
||||
NOISE SOURCE |
NOISE EXPOSURE CATEGORY (NEC) |
|||
A |
B |
C |
D |
|
Road Traffic 07.00-23.00 23.00-07.001 |
<55 <45 |
55-63 45-57 |
63-72 57-66 |
>72 >66 |
Rail Traffic 07.00-23.00 23.00-07.001 |
<55 <45 |
55-66 45-59 |
66-74 59-66 |
>74 >66 |
Air Traffic2 07.00-23.00 23.00-07.001 |
<57 <48 |
57-66 48-57 |
66-72 57-66 |
>72 >66 |
Mixed Sources3 07.00-23.00 23.00-07.001 |
<55 <45 |
55-63 45-57 |
63-72 57-66 |
>72 >66 |
0 NOISE LEVELS: The noise level(s) (LAeq,T) used when deciding the NEC of a site should be representative of typical conditions.
1 NIGHT TIME NOISE LEVELS (23.00-07.00): Sites where individual noise events regularly exceed 82 dBLAmax (S time weighting) several times in any hour should be treated as being in NEC C, regardless of the LAeq,8h (except where the LAeq,8h already puts the site in NEC D).
2 AIRCRAFT NOISE: daytime values accord with the contour values adopted by the Department of Transport which relates to levels measured 1.2m above open ground. For the same amount of noise energy, contour values can be up to 2 dB(A) higher than those of other sources because of ground reflection effects.
3 MIXED SOURCES: this refers to any combination of road, rail, air and industrial noise sources. The “mixed source” values are based on the lowest numerical values of the single source limits in the table. The “mixed source” NECs should only be used where no individual noise source is dominant.
To check if any individual noise source is dominant (for the purposes of this assessment) the noise level from the individual sources should be determined and then combined by decibel addition (remembering first to subtract 2 dB(A) from any aircraft noise contour values). If the level of any one source then lies within 2 dB(A) of the calculated combined value, that source should be taken as the dominant one and the site assessed against the appropriate NEC for that source, rather than using the “mixed source” NECs. If the dominant source is industrial noise see paragraph 19 of Annex 3 of PPG24.
If the contribution of the individual noise sources to the overall noise level cannot be determined by measurement and/or calculation, then the overall measured level should be used and the site assessed against the NECs for “mixed sources”.
< Previous | ^ Top | Next >