34
Chapter 5
Frequency analysis
What can be done to the measured data?
Data acquired are available for inspection,
during or after a measurement.
You may:
• Switch between sound level meter display and
frequency spectrum display
• Display the functions measured
• Display the result tables
• Change the spectral weighting function between
A- and C- or Z-weighting, this depends on which
one you have selected
• Display the eight percentiles (requires the pres-
ence of the optional extension 4) and set one of
them as you like
• Store the results for future use
The measurement time elapsed counter will be up-
dated to reflect the back erase time. The statistics buff-
ers (optional extension) as well as all other measured
parameters will be updated accordingly.
Displaying the functions measured
The instrument measures the A-weighted and C- or Z-
weighted SPL, L
MAX
, L
MIN
, L
eq
, L
E
and the L
PEAK
. Note
that the SPL, L
MAX
and L
MIN
are all measured with the
selected time constant while the other values are not
dependant on this.
The same functions are available in the frequency
analysis with the exception of L
PEAK
. The peak level is
not measured per frequency band. In addition, T
Max5
is
not available for frequency analysis (applies to units
equipped with the optional extension 0).
However, since the frequency analysis is made in
parallel with the traditional (A- and C- or Z-weighted)
sound level measurement, the broadband peak
levels and the T
Max5
levels are still assessed during the
measurement.
No
SPL
after the measurement
During measurements the SPL value is updated eve-
ry second. Once the measurement is over, the SPL
becomes meaningless. A single SPL value cannot
be used to characterise the measurement unless it
represents some kind of maximum, minimum or time-
integrated average. It is thus not accessible
post-
measurement
.
To return to ready mode, i.e. how the instrument
behaved before the measurement was started press
the
EXIT
key. You will be prompted to store the data or
press
EXIT
again. In both cases the instrument will go
back to ready mode. The SPL will now be displayed
again.
If you choose not to store the data by pressing
EXIT
again, the measured data will be lost beyond
retrieval.
Displaying the result tables
As an alternative to the procedures shown on the next
page, you may display all the measured data in tables.
Press the
TBL
key to enter table mode. Note that the
look of the tables depends on whether you start from
sound level meter display mode or from frequency
spectrum mode.
The tables are available during, as well as after a
measurement. Remember that SPL values are shown
during the measurement only.
The tables available are shown in the side bar
Displaying the result tables
.
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