Norsonic NOR150, Instruction Manual

Page: 31 / 216

15 Norsonic Nor150
Instruction Manual
Figure 4.2 - The Function cube expresses a three-dimensional
space with the data type (e.g. SPL), the time constant (e.g.
F) and the spectral weighting (e.g. A-weighting) as the
dimensions. A function will then be a point in this space. Note
that not all the points in this space are defined. For example,
the (normal) L
eq
has no time constant and for the Nor150 the
peak is not defined in octave and third octave bands.
The analyser does either full octave or third-octave
analysis – it cannot do both simultaneously.
Special measurement function used in Building
Acoustic, Sound Intensity mode, or other modes,
are not discussed in this chapter.
Filling in the three dimensions with data types, time
constant and spectral weighting, we arrive at the
Function cube.
So far we have yet to mention statistics. In the Nor150
statistics are either based on SPL using a user defined
time constant or Leq. The statistics can be presented in
several ways – as statistical and cumulative distribution,
but also as percentiles. There are 8 percentiles settings
available. This must be set up in advance before a
measurement.
The spectral weighting functions A, C and Z are
measured simultaneously and in addition to the 1/3 or
1/1 octave filter bands (optional).
FFT (optional) can be measured simultaneously with
1/1 or 1/3 octave filter bands
Statistics can be calculated for Global values and for
the time profiles A and B, and for the Moving (sliding)
L
eq
function.
Ln cannot be selected simultaneously for Global and
Profile B or Moving Profile, since they are based on
different measurement functions. Profile A and Global
uses SPL (either Fast or Slow – selectable) while
Profile B and Moving Profile uses Leq as base for the
calculation of Percentiles.
All three time constants (exponential averaging), Fast,
Slow and Impulse are measured in parallel.
The instrument measures all parameters both as global
values and time profile values also in 1/1 octave band or
1/3 octave bands, if applicable. The user may configure
which parameter to measure in order to limit the amount
of data.