Norsonic nor140, Instructional Manual

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146
Chapter 24
Building Acoustics
procedure trying to make the excitation signal as flat
as possible. The obtained spectrum shape is stored
in the instrument and can later be turned off and on
as desired.
No error message is given if the max attenuation
of 12 dB is insufficient for the purpose, but the excita-
tion signal spectrum is still usable and improved with
respect to the requirement of the standard.
For Reverberation time measurements, the settings
for the equalizer will not be used.
Impact sound insulation
Impact excitation
The impact sound shall be generated by the standard
tapping machine as specified in ISO 16283-2 Meas-
urement of sound insulation in building and building
elements – Part 2: Field measurement of sound insula-
tion of floors. For isotropic floors, a single position for
the tapping machine near the middle of the room is
sufficient for measurements according to ISO 10052.
For other measurements more positions are required.
Norsonic recommend the tapping machine Nor277.
Measurement of sound level
As stated in the standards, the spatial average of the
sound level in the receiving room is required. For sur-
vey measurements according to ISO 10052, this may
be achieved by measuring the level while moving the
sound level meter (microphone) around in a figure-of-
eight trajectory. Recommended measuring time is 30
seconds. For the engineering method according to
ISO 16283-2, point by point measurements has to be
applied and the instrument will calculate the averaged
level.
The level may be measured in the normal mode of
operation and the results stored for later processing.
Alternatively, the measurement may be started from
the calculation menu when the result is required for the
calculation. Press
SETUP
to enter the menu for setting
the measurement time.
Reverberation time
For a survey measurement according to ISO 10052,
the corrections for the acoustic absorption may either
be based on measurement of the reverberation time
or based on information about the room type, type of
surface and furniture. Both methods are implemented.
For measurements according to the ISO 16283 series of
standards, the reverberation time has to be measured.
If a measurement is required, the reverberation time
may be measured in the reverberation mode and the
result stored for later processing (MODE 2. Rev.). Al-
ternatively, the measurement may be started from the
calculation menu when the result is required for the
calculation.
Calculating the Survey result
Select the building acoustic mode and press
2
for
“Impact”. Enter the value for the room volume “V”
and press
ENTER
or move the field cursor to “C” and
press
ENTER
for a calculator. The calculator allows
you to enter the length, width and height of the room in
order to calculate the volume.
The field cursor automatically moves between the
fields as values are entered. If you want to adjust any
previously entered value, use the arrow keys to move
the field cursor to the wanted parameter.
The next set of values to be entered is the sound
levels in the receiver room L for each octave-band.