Crystal Instruments Spider - Page 243

Spider DSA User’s Manual
243
Frequency
Weighting
Filter
Time
Averaging
RPM or
Time
based?
RPM-based
buffer
Raw
data
Time-based
buffer
Figure 152. Time averaged sound level computation.
The table below shows the symbols for the time-average sound level. In the time
averaging sound level measurement, frequency weighting can be selected as A, B,
C or Z. The time interval for time averaging can be set to any value between 1
second and 24 hours.
Frequency
Weighting
Z
A
B
C
Symbol
L
eq
L
Aeq
L
Beq
L
Ceq
Peak sound level
Only C-weighted and un-weighted signals are available for peak sound level as is
required by the standards.
Symbol
L
peak
L
Cpeak
Sound exposure level
Sound exposure level and time-average sound level have the same frequency
weighting and same time interval.
Frequency Weighting
Z
A
B
C
Symbol
L
E
L
AE
L
BE
L
CE
Statistical level: value reading
Any statistical level L
N
is the sound level which is exceeded for N% of the defined
measurement duration.
Symbols for L
N
,
N = 1, 5, 50, 95
L1
L5
L50
L95
Input Channel Time Streams
In the Spider, time domain data is always available in the form of a long-time
history. The user can view and record the time signals, but the sampling rate of