BRUEL & KJAER 4226 User Manual page 28

20 Multifunction Acoustic Calibrator Type 4226 – User Manual
Since this is a check only of the electronics (and/or electromechanics) providing the F and S
functions, the type of microphone, if any, fitted to the measuring instrument is immaterial. The
check is merely a comparison of two values, maximum and constant, measured under the same
conditions.
Table 3.3
Maximum response to
test tonebursts in
Characteristic
relation to the
response to the
continuous signals (in
decibels) for F and S
time weighting
functions
The compression circuit of Type 4226 is disengaged for this check since it is inapplicable in the
generation of a limited toneburst. This also means that the steady-state level will require manual
adjustment after each change of frequency. The default frequency is 2000 Hz, but other
frequencies may be selected at the time of adjusting the steady-state level.
The instructions below use a sound level meter as the instrument under test. The principal,
however, applies in general.
Ensure that both Type 4226 and the sound level are switched on.
1) Set up the sound level meter as follows:
a) Set to measure SPL (sound pressure level).
b) Set the dynamic range to a range that will prevent overload at 114 dB SPL.
c) Set the frequency weighting to Lin or aW.
d) Set the time weighting to Fast or Slow.
2) Fit the coupler onto the microphone of the sound level meter, press it down gently until the
microphone is properly seated against the stop in the coupler. Ensure that the coupler is
properly connected to Type 4226.
3) Set up Type 4226 as follows:
a) Set the
Function
4) The 2 kHz LED on Type 4226 will light up. This is the default frequency setting for this test.
Other frequencies may be selected using the
5) When conditions are stable, rotate the knurled wheel on Type 4226 until the Sound level
meter displays a constant level of 106.0.
6) Set the
Function
the setting in step 1c. This will cause the LED of the selected frequency to flash at regular
intervals.
Maximum
Detector Response re
Continuous
Signal
F –1.0
S –4.1
switch to Test Level. This will enable the
switch on Type 4226 to Time Weighting F or Time Weighting S to match
Tolerances on response
Type 0 Type 1
±0.5 dB
+1
±0.5 dB
±1
Frequency Step
buttons.
Frequency Step
Type 2
+1
–2
±2
buttons.