Night noise guidelines for Europe - WHO/Europe - World Health ...

APPENDIX 2. RELATIONS BETWEEN L NIGHT AND
INSTANTANEOUS EFFECTS
STATEMENT 1
APPENDICES 137
Let f be a function of SEL that gives the expected number of instantaneous effects
caused by a single event. With a given L night and a given number of events N, the
expected number of times that an effect occurs in the night, n, is maximal if all events
have equal SEL, provided that f°10lg is increasing but negatively accelerated.
STATEMENT 2
If
n max = 10 (L night -SEL+70.2)/10 . f(SEL),
has a maximum over SEL and f is the quadratic function f(SEL) = a SEL 2 + b SEL
+ c, then the maximum occurs irrespective of L night at
SEL 0 = 4.34 – A ± ((A – 4.34) 2 – (c/a) + 8.68A) 1/2 ,
where A = b/(2a). (Only with + at the place of ± the value will come in the realistic
range of SEL)
STATEMENT 3A
If the shape of the time pattern of the sound level has a block form, then SEL = L Amax
+ 10lg(T), where L Amax is the maximum sound level (integrated over 1-s) and T is
the duration of the noise event in seconds.
STATEMENT 3B
If the sound level increases with rate a (in dB(A)/s) and after time point t = 0 decreases
with rate –a, then SEL≈L Amax – 10lg(a) + 9.4.
NIGHT NOISE GUIDELINES FOR EUROPE