Norsonic nor1218, Instruction Manual

11

Norsonic Nor1218

Instruction Manual

Frequency response

The figure below shows the typical frequency re-
sponse for sound approaching the microphone in two 
directions. The response marked “Vertical” is the re-
sponse for sound approaching the microphone from 
above along the bird spikes, when the microphone is 
in the recommended vertical direction. The response 
marked “Horizontal” is the response for sound ap-
proaching the microphone in a horizontal direction 
when the microphone is mounted in the same recom-
mended vertical direction.
Due to the lower sensitivity for higher frequencies, as 
shown on the figure, it is recommended to correct the 
frequency response to ensure that the response is 
within the requirement for Class 1 sound level meters 
specified in the international standard IEC 61672-1.

10

100

1k

10 k

20 k

30

−

25

−

20

−

15

−

10

−

5

−

0

5

10

Vertical

Horizontal

Sensitivity level [dB]

Frequency [Hz]

When the microphone system is used in connection 
with the precision sound level meter Nor131 or Nor139 
(for program version 3.0 and above), select 1218 Verti-
cal or Horizontal in the input setup menu to enable the 
right settings. If the large windscreen Nor4576 is fit-
ted above the standard windscreen supplied with the 
Nor1218 an extra frequency compensation is needed. 
This is only possible if the horizontal mode is selected. 
Select 2: corrections in the input menu and then 1: 
large windscreen in the next submenu to turn this cor-
rection on. Please note that this correction is always 
set to OFF each time the instrument is turned off. 
There is not possible to use large windscreen if ver-
tical mode is selected. Adding the extra windscreen 
is required in some applications when measuring on 
wind turbines.