Norsonic nor140, Instructional Manual, Page: 166 / 220

148
Chapter 24
Building Acoustics
2. It is not allowed to use the pre-defined reverberation
times based on the room criteria. The reverberation
times must be measured in the actual receiving
room.
3. If the measured reverberation time for any frequen-
cy band is outside the 0,4 – 2,0 seconds range, the
value in the calculation is changed to the shortest or
longest value of the mentioned range. This means
that the measured value of 0,32 s will be replaced
with 0,4 s, and the measured value of 2,8 s will be
replaced with 2,0 s in the calculations. This corre-
sponds to a reverberation index k that always is in
the range -1 to +6 dB.
Calculating the impact sound insulation
according to the Engineering method
Use the
MODE
button to select the building acoustic
mode and press
4
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.
Receiving Room Level
The next set of values to be entered is the sound levels
in the receiver room L for each one-third octave-band.
Recall a measurement by using the
RECALL
key or
press
START
for starting a measurement. If measured,
the values are automatically stored.
You are prompted to accept the recalled or meas-
ured values as a part of the averaged result. Press
ENTER
(alternatively
STORE
) to accept or
EXIT
(al-
ternatively
DEL
) if you don’t want to accept. You may
repeat the loading of data to obtain the averaged re-
sults from more measurements. The number of meas-
urements that has been accepted for the averaging is
displayed by a number N. Press the
TBL
key to display
the averaged levels.
The averaged level L is obtained according to the
following formula where L
k
is the result from each of the
N measurements:
Display of measurement result