Checking The "F" And "S" Time Weighting - BRUEL & KJAER 4226 User Manual

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
b) Set the
Sound Level
✐
The settings of the Microphone and Sound Field switches are immaterial as long as they
Please note:
remain unchanged throughout.
4) Select the first frequency of interest on Type 4226.
5) When conditions are stable, note the reading displayed on the sound level meter.
6) Set the
Sound Level
the reading displayed on the sound level meter.
7) Set the
Sound Level
the reading displayed on the sound level meter.
8) Reset the
Sound Level
9) Repeat steps 5 to 8 for the remainder of the frequencies of interest.
10) For each selected frequency, determine what differences exist between the observed
displayed levels and the expected displayed levels (separated by 10 dB steps) and check
these against the tolerances shown in Table 3.2.
3.7

Checking the "F" and "S" Time Weighting

Type 4226 may be used to check the F (fast) and S (slow) time weighting functions of sound
measuring instruments, measuring amplifiers, level recorders, etc. Type 4226 does this by
providing the requisite test tonebursts for determining the onset transient characteristics of F
and S detectors.
In relation to the response to the continuous signal (steady-state level of the tone burst), IEC and
ANSI standards define an acceptable response to the tone burst itself. The response is defined by
how much the maximum rms response to the toneburst is allowed to fall short of the rms
response to the continuous signal. Table 3.3 shows the maximum response to test tonebursts in
relation to the response to the continuous signal for type 0, 1 and 2 sound level meters.
The first stage of the checking procedure requires the steady-state level of the tone burst to be
adjusted to 4 dB below the upper limit of the instruments rms primary indicator range, that is,
4 dB below its full-scale deflection. The second stage requires observing the maximum indicated
reading on application of the toneburst.
switch to Calibration.
switch to 94 Lin.
switch on Type 4226 to 104 Lin and when conditions are stable, note again
switch on Type 4226 to 114 Lin and when conditions are stable, note again
switch to 94 Lin and select the next frequency of interest.
CHAPTER 3
19
Operation