Norsonic nor118, Instruction Manual, Page: 18 / 116

6 Chapter 1
Introducing the Nor118
7 Norsonic Nor118
User Guide
Time profile measurements
Remember the time when paper-based level recorders
used to be the only way to capture the time profile of a
sound measurement? Remember the struggle we all had
with calibration and proper scaling of the plotting on the
paper?
With Nor118 instruments equipped with the optional
extension 6 you will be able to retain all the advantages
of the level recorder principle, while at the same time
discarding all the trouble!
No paper – no trouble.
e optional extension  – level
vs. time – records the time profile of the -weighted equiv-
alent level, the -weighted maximum sound pressure level
and the - or -weighted peak level – simultaneously!
e principle is based on dividing the measurement into
periods of identical duration. e period duration can be
from 1 second and upwards in 1 second steps (from 100ms
in enhanced mode).
When a level vs. time measurement is running, the
equivalent level will be calculated per period, thus giving
you the time profile for the measurement.
e  and the  levels are also recorded per
period so that all three functions will yield a value for
every period. Everything is retained within the instru-
ment, hence there is no paper involved in the process!
When you are going to make a measurement, the
maximum number of periods at your disposal will depend
entirely on the amount of free memory available. It will by
no means depend on the duration of each period. is is
because a period is a period in the sense that it will occupy
a fixed space in the memory, irrespective of its duration.
Given the large memory of the Nor118 – the memory
can hold approximately 2 500 000 values – the period dura-
tion will for all practical cases be determined by your need
for time resolution.
Provide details – maintain overview.
e level vs. time
feature is the tool you need for detailed analysis of the
time profile. However, a measurement failing to provide
an overview of the entire analysis cannot be accepted.
So, we added a global analysis to all time profile meas-
urements. It just runs in the background and makes little
fuzz about its presence.
Switching between  and  is easy, a dedi-
cated key on the front panel – the Σ - ∆ key – lets you toggle
between the two. e Σ (pronounced “sigma”) denotes the
global analysis while the ∆ (pronounced “delta”) denotes
the time profile.
Consequently, when you have set up for a time profile
measurement by defining the total duration and the time
resolution, you have in fact prepared the instrument for
two parallel measurements – the global and the profile!
Absolute vs. relative time.
If exact time information is
important, just put the instrument in absolute time mode
by pressing the key  t. All periods will then have the
date and time of day they were acquired displayed. If time
elapsed since start is sufficient push the key again to return
to relative time. is is a display function – the absolute
time is always recorded for all measurements.
Setting up is easy to do.
After you’ve defined the
duration and the resolution, all you need to do before
you press the  key, is to define the time constant
and whether to use - or -weighting as the secondary
spectral weighting function.
During the measurement you have instant access to the
global analysis and profile. For each of these the function
key lets you inspect all the functions measured.
For the global analysis the functions measured are