Norsonic NOR150, Instruction Manual

Page: 96 / 216

80 Chapter 20
Building Acoustic
Level - Setup (Figure 20.16)
• Level Duration is used for pre-setting the
measurement duration for the source and/
or receiving room level measurements. Most
Standards require 15 s for measurements down to
50 Hz and 6s for measurements down to 100 Hz.
•
Background noise Duration
is used for pre-setting
the measurement duration for the background noise
in the receiving room.
•
Filter
enables the user to switch between 1/3- and
1/1-octave measurements. Please note that for all
but one currently supported building acoustics
testing Standards in the Nor150 system, only the
1/3-octaves are selectable. If ISO 10052 is the
selected standard, the bandwidth is automatically
set to 1/1 octaves and set back to 1/3 octaves in all
other cases.
Lower frequency
is used for selecting the lowest
frequency band to be measured. In the BA mode,
the minimum is 0,4 Hz for 1/3-octaves.
Upper frequency is used for selecting the highest
frequency band to be measured. In the BA mode,
the maximum is 20 kHz for 1/3-octaves.
•
Source Position
is used for indicating the different
loudspeaker or tapping machine positions. This
may be a requirement by the standard. Instead
of entering this setup menu to change the source
position, use the
#
soft key in SPL mode display
(Figure 20.17).
Reverberation - Setup (Figure 20.18)
•
Filter
enables the user to switch between 1/3- and
1/1-octave measurements. Please note that for all
but one currently supported building acoustics
testing Standards in the Nor150 system, only the
1/3-octaves are selectable. If ISO 10052 is the
selected standard, the bandwidth is automatically
set to 1/1 octaves and set back to 1/3 octaves in all
other cases.
•
Excitation Type
is used for selecting the actual
method for detecting the correct decay. Noise is
used for operation with the internal noise generator,
and Impulse is used for operation with an external
impulsive signal. When used with Impulse, the
Nor145 will always calculate the reverberation times
based on the backward integrated decay.
•
Duration
is setting the time duration of the active
noise excitation before the decays are measured.
•
Trigged at
is setting the start point for the
reverberation time calculation. “5 dB level below”
starts below the calculation 5 dB below the excitation
noise level (or max level at impulse excitation). “100
- 300 ms” normally starts at 5 dB below but adjust
this point to be within a 100 - 300 ms range after
excitation noise is turned off.
Figure 20.16
Figure 20.17
Figure 20.18