Svantek SVAN 958A - D.4. STATISTICAL LEVELS - LN% DEFINITION

299
SVAN 958A User Manual
EAV Time Left
Current time to reach Exposure
Action Value during the
measurement
TEAVEAV
TTTL
− =
ELV Total
Time
Current time to reach Exposure
Limit Value during the
measurement







=
75.1
TTV
2
TTA
TT
s
m
in is limitELV if ELV
s
m
in is limitELV if ELV
ELV
where
2
WB
A
0TTA
RMS
ELV
TELV








=
4
WB
V
TTV
VDV
ELV
TELV








=
ELV Time Left
Current time to reach Exposure
Action Value during the
measurement
TELVELV
TTTL
− =
D.4. STATISTICAL LEVELS – LN% DEFINITION
The noise level L(t) is the continuous random variable.
The probability that the temporary noise level L(t) belongs
to the interval
LL,L
kk
+
is called the class density
and it can be expressed by the equation:
( )  
PtLLtLLP
n
1i
ikkk

=
 =  +  
where:
i
t

- time intervals, in which the noise level
( )
LL,LtL
kk
+
occurs,
L 
- so-called class interval or distribution class
of the series,
P
- total observation period.
In case when the class interval approaches infinity, the probability of L(t) tends to the probability of
k
L
. In
practice,
L 
value is strictly determined and it depends mainly on the dynamics of the measurements
performed in the instrument. There are 120 classes in the instrument and the width of each class is equal to
1 dB. The histogram is the set of the class density values calculated for all classes.
The statistical distribution function, which determines the
probability (expressed in %) of the noise occurrence on
the level equal or less than
LL
k
 +
is given by the
formulae:
( )
 
( )

=
=
j
1k
kj
LPLtLP
The cumulative density function, expressed by the
equation:
( )
 
( )
 
jj
LtLP1LtLP −=