7.1.3. Statistical Distribution
of
Sound
or
Vibration Levels
An extension
of
the
range
of
application
of
the
Level
Recorder
is
the
Statistical Distribution Analyzer
Type
4420,
which,
with
input
from an
instrument such as the
Sound
Level
Meter, may be used for collecting
statistical
data on noise and vibration.
The
Statistical Distribution Analyzer
consists mainly
of
a pulse generator and thirteen digital counters. The pulses
are distributed
to
twelve
of
the
counters
by
the
writing arm of
the
Level
Recorder Type 2305,
the
writing width
of
which
is
divided into ten bands
(see Fig.7.3). Since
the
writing width of
the
Level Recorder corresponds
to
either 10,
25
or
50 dB, depending
on
which range potentiometer
is
em-
ployed,
the
degree
of
statistical resolution can be selected accordingly.
The
thirteenth
counter counts
the
total elapsed time, so
that
relative distribution
curves can be constructed from
the
data provided
on
the
counters.
Connection
of
instrumentation for these measurements
is
shown in
Fig.7.4.
Units
of
time
(Counts)
Sound Pressure
Level
Fig.7.3. Presentation
of
data
from
Statistical
Distribution
Analyzer
<
~~
~
;
·
·
-
~
·
.___:_:.__:__
2209
., -·
-~~
}
:!i
,
~
"
.
,;
.
;
ii!
1::::-:::
-
::::
--i: .-
;J
<,·
•t:
~
·
~r~
§
:<-
~L--l
~
1
~
1
·L_j1,.....-----~
:
ili
.
2305
4420
17
212
1
Fig.7.4. Connection
of
the Statistical
Distribution
Analyzer
93
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