Calibration Of The Ear Simulator - BRUEL & KJAER HF HATS 5128 User Manual

2.5

Calibration of the Ear Simulator

Prior to calibrating the ear simulator, the associated connector 'Right ear' or 'Left ear' shall be
connected to an audio analyzer, see Fig.2.2. The ear simulator is equipped with a pre-polarized
microphone, hence no external polarization voltage is required. Each ear simulator can be
calibrated using the Sound Calibrator Type 4231. Type 4231 provides a 1 kHz sinusoidal tone
(±1.5%) with a level accuracy of ±0.3 dB.
✐
The calibration procedure is the same for the left and right ear.
Please note:
The microphone is an integral part of the ear simulator and must not be removed from the
ear simulator assembly.
To calibrate the ear simulator, use the following procedure and refer to the relevant steps in
Fig.2.6:
1) Release the complete ear simulator by pressing the button located on the neck of Type 5128.
2) Remove the coupler from the ear simulator by unscrewing the plastic nut.
3) Fit the calibrator adapter DI-0658 onto the coupler and secure it using the plastic nut.
Be careful not to damage the thread of the nut. Do not use excessive force and make sure
CAUTION:
that the threads in the two pieces engage properly before you screw in the calibration
adapter. Do not over-tighten. Do not touch the microphone diaphragm.
4) Fit the calibrator onto the adapter. Ensure that it is pushed firmly over the end of the adapter.
5) Switch the calibrator on.
6) Adjust the sensitivity of the measuring instrument to display the correct sound pressure level,
as indicated in Table 2.1
for the audio analyzer being used for the measurement.
Table 2.1
The actual sound
pressure level at the
microphone
diaphragm when using
Calibrator Type 4228
or Type 4231 with
Calibrator Adapter
DI-0658
*Supplied with Type 5128-C.
†Supplied with Pistonphone Type 4228.
‡'Stated SPL' is the sound pressure level stated on the calibration chart (BC-0195) of Type 4228. The
nominal SPL of Type 4228 is 124 dB.
'L
UZ-0004 suppled with Type 4228.
1 The value in Table 2.1 differs from the sound pressure level given in the instruction manual for the
calibrator. This is because the actual sound pressure level at the microphone diaphragm is influenced
by the coupler.
1
. The procedure for doing this is described in the instruction manual
Calibrator
Pistonphone
Type 4228
Sound Calibrator
Type 4231
' is the correction for the ambient pressure, which can be read directly from Correction Barometer
p
Adapter
*
DI-0658 and
†
DP-0776
*
DI-0658
CHAPTER 2
Operation
Corrected Output
Level (SPL)
Stated SPL +
‡
– 0.7 dB
L
p
95.2 dB
9