BRUEL & KJAER 2221 - Measurement Examples

After a measurement period of 3 hours the displayed SEL is 98 dB(A). For a measurement
period of 3 h, the conversion table gives a SEL- Leq = 40,3 dB. The Leq for 3 hours is then
98- 40,3 = 57,7 dB(A)
3.5.8.
Noise Dose Evaluation
The
percentage of the noise dose for a range of "Allowed 8 hours Leq" values is easily ob-
tained from the SEL using the nomogram given in Fig.3.9. The SEL value is read directly
by the 2221/22.
Allowed 8 hours
L eq -value
80 dB
85
/
90
/
/
3.5.9. Example of Measurement
/
/
/
/
/
Noise dose in % of
max. allowable dose
/
/
/
1000% /
800 /
400
/
/
200
/
100%
0
/
/
/
SEL -value
dB
/
/
/
Fig. 3.9. Noise dose determination
135
130
125
120
115
110
771030 / 1
This example is intended to illustrate pratically the differences between the four different
functions available on the 2221/22. The measurements were carried out on noise pro-
duced by an electrical typewriter using the Type 2222. Similar results would be obtained if
Type 2221 was used.
Max.
Max.
Trial
Leq
SEL
"Slow" "Peak"
dB(A) dB(A) dB(A) dB( Lin.)
1
1 min.
62,8 80,6
75,2 93,6
(Slow
Typing) 3 min.
62,8 85,3
75,2 93,7
2
1 min .
68,1
85,9
82,0
93,6
(Rapid
3 min.
63,4
86,0 82,0 93,6
Typing)
811147
Table 3. 1. Measurement results from the example
17