BRUEL & KJAER 4226 User Manual page 17

corrections for the reference microphone are not applied. The compression (feedback) loop,
however, remains in force to ensure a stable sound level in the coupler
•
Frequency Step:
With the Function switch in Test Level or Calibration mode, use these buttons to step Up or
Down the test signal frequencies or to select to use an external generator. Press and hold
either button to cycle through the range.
✐
Test Level or Calibration must be selected to activate these buttons.
Please note:
•
Function:
Use this switch to select the test-sound signals in the coupler for one of the following sound
level meter function checks:
✐
Unless changed manually, the preselected Frequency Hz setting of 2 k will prevail.
Please note:
– Crest Factor: The sound signal produced in the coupler will check the crest factor
handling of the sound level meter. The sound level produced in the coupler will have a
crest factor (that is, a peak-rms ratio) of 3. The rms level is set using the Test Level setting
(when the level is stable, switch to Crest Factor). See section 3.8 to find out about crest
factor set up and handling, including the rms detector accuracy for instruments in
accordance with IEC 60651 and ANSI S1.4-1983. The crest factors quoted here are valid
only at 2 kHz and above
✐
An electrical signal with a crest factor of 10 is available via the AC Out socket on the side
Please note:
panel.
– Time Weighting F: The sound signal produced in the coupler will check the "F" (fast) time
weighting of a sound level meter. The signal is a 200 ms tone burst occurring every two
seconds. The level of each tone burst is set using the Test Level setting (when the level is
stable, switch to Time Weighting F). Between each tone burst, the level will drop by 20 dB.
See section 3.7 to find out more about checking the time weighting
– Time Weighting S: The sound signal produced in the coupler will check the "S" (slow)
time weighting of a sound level meter. The signal is a 500 ms tone burst occurring every
eight seconds. The level of each tone burst is set using the Test Level setting (when the
level is stable, switch to Time Weighting S). Between each tone burst, the level will drop
by 20 dB.
See section 3.7 to find out more about checking the time weighting
– Test Level: The sound level produced in the coupler can be adjusted over a 20 dB range
using the knurled wheel. The frequency is preset at 2 kHz, but other frequencies may be
selected. When this function is selected, the compression circuit, which otherwise
ensures a well-defined constant level at each frequency, is deactivated. Therefore, do not
use this function for checking frequency response.
– Calibration: This function is for checking the acoustic sensitivity and frequency response
of a sound level meter. When selected, use the switches marked Microphone, Sound
Field and Sound Level dB to set up.
This setting also activates the compression circuit that ensures a well-defined constant
level at each frequency. For more information, see sections 3.4 to 3.6.
The Parts of Multifunction Acoustic Calibrator Type 4226
CHAPTER 2
9