HT instruments SPEED418 - Manual (Page 54)

400 Series
EN - 53
7.1.1. dB mode
3. Connect the sound level probe to the instrument’s optical input by means of the optical cable
4. Press the GO/STOP key. The instrument starts
measuring the acoustic pressure. The following
values are displayed:
 SPL
acoustic pressure
 Peak acoustic pressure peak
 Duration time elapsed since the
beginning of the recording
A U X
S P L - - - - d B
P e a k - - - - d B
D u r a t i o n 0 0 0 0 : 0 0 : 0 0
dB
Func
5. Press the GO/STOP key again. The instrument
stops measuring and displays the following
values:
 Leq
equivalent level of acoustic
pressure
 Peak acoustic pressure peak
 Duration duration of the recording
A U X
L e q - - - - d B
P e a k - - - - d B
D u r a t i o n 0 0 0 0 : 0 0 : 0 0
dB
Func
The equivalent level of the acoustic pressure is defined as:
2
0
0
2
10
1
log 10
P
dt P
T
Leq
T
i


where: P
0
is the reference pressure, ca. 2 10 5 Pa
P
i
is the instant pressure of the acoustic range
In praxis, the following formula is used:
N
N
Leq
N
i
L
i
i 
 
1
10
10
10
log 10
where: L
i
is the sampled level [dB]
N
i
is the number of samples measured for the L
i
level
N is the number of samples measured
6.
7. Please note that Lep, the personal exposure level, is defined as the equivalent level of
the acoustic range a person is exposed to during a normal workshift (8 hours). "Lep"
coincides therefore with "Leq" calculated for 8 hours.
8. Once recording is completed, measures can be saved by pressing the SAVE
key twice or the SAVE key and, subsequently, the ENTER key (§ 9.1)