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Norsonic Nor150
Instruction Manual
The instrument is capable of measure all three available
time weighting filters A, C and Z in parallel. You may
also define which of the filters that shall be used in idle
mode (readymode).
Filter On/Off.
Turns the real time 1/1 or 1/3 octave band
filters on/off. You also select frequency range for the
filters.
The Frequency Weightings networks are not affected
by the frequency range setting of the 1/1 or 1/3 octave
band filters since they are true weighting networks and
not calculated from the 1/1 or 1/3 octave band filters.
FFT On/Off.
Turns on the FFT feature. The FFT
calculation are performed in parallel with the 1/3 or 1/1
octave band.
Select either 1.46Hz / 16384 lines or 2.93Hz / 8192
lines. Upper frequency is 22000Hz. This setting is
independent of the frequency range setting of the 1/1
or 1/3 octave bands.
Please note: The Frequency Weightings are not
affected by the frequency range setting of the 1/1 or
1/3 octave bandfilters since they are true weighting
networks and not calculated from the 1/1 or 1/3
octave band filters. One limitation should however
be observed. An analogue high pass filter is enabled
at 6,3 Hz if the if lower frequency of the 1/3 octave
or 1/1 octave filter is set above 6,3Hz. You don’t need
to consider this for the A and C filter due to the high
attenuation at low frequencies. The Z filter has a
zero response and will follow the analogue HP filters
attenuation at low frequencies. The Frequency range
response of the FFT will also follow the response of
the analogue highpass fiter.
High-pass input filter
The instrument is equipped with an analog high-pass
filter to reduce noise from wind or other sources with
frequencies in the lower end of the frequency range.
The filter is automatically turned on when the 1/1- or
1/3-otave filter is set equal to or higher than 6,3 Hz and
turned off when a lower frequency is selected.
When this filter is “Off” the lower frequency response
is -3 dB at 0.08 Hz (or -0.5 dB at 0.25 Hz). The setting
of this filter may have a great influence especially on
the Z network and low-frequency band filtered levels.
Filter type:
3rd order HP filter (-3 dB at 3 Hz, Butterworth
response).
For instruments without octave band filter, the highpass
filter is always on.
Figure 9.2
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