Norsonic nor118, Instruction Manual

Page: 83 / 116

70 Chapter 13
Measuring the sound power
71 Norsonic Nor118
User Guide
lows the exactly the same procedures as the sound power
measurements.
However, the background noise level will in most
situations vary little from one microphone position to
another, it will therefore normally be enough to measure
the background noise level for one typical microphone
position.
To toggle between the measurement control display and
the background noise measurement control display:
• Use the  key.
Measurement surface
e sound power calculation requires the operator to select
the correct measurement surface.
To select the right measurement surface:
1
Press the  key and choose the corresponding
selection in the sound power setup menu. e selected
surface is indicated by  for  and 
for  with an additional  or  for
test objects placed against a  or in a .
e selected surface is also indicated by a simple dia-
gram.
2
Depending on the selected surface, the measurement
radius or the distance from the reference box (i.e. the
minimum box that fits around the test object) must be
keyed in. e calculated area S of the total measurement
surface will then be displayed.
3
Finally, key in the acoustic environment correction

2.
Sound power results
Based on the averaged sound pressure level of all the
microphone positions, the measured background noise
level and the selections and corrections made in the
sound power setup menu, the Nor118 will display the
final 
W
.
To see the sound power calculation results:
• Press the  key.
• In addition to the overall results, the impulsive noise
values, the 
PEAKC
(or 
PEAKZ
) level and the noise direc-
tivity of the test object for all microphone positions are
found by sequential pushes of the  key.
e results may also be copied to a printer. e report
includes necessary spaces for all the required measurement
information to be written directly on the report by the user.
On a second page, the individual results for each of the
microphone positions are printed. See Making hardcopies
for more on this.
On the previous pages you will find display examples
together with the calculation procedure for the determi-
nation of the environmental correction factor 
2
, which
has been repeated from the previous chapter for your
convenience.