BRUEL & KJAER HATS 4606, User Manual

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High-frequency Head and Torso Simulator (HF HATS) Type 5128 – User Manual 20
The loudspeaker has a maximum voltage rating for continuous operation of 0.7 V
rms
. To reduce
the risk of damage, the drive to the loudspeaker is limited by a protection circuit mounted in the
head of Type 5128. The loudspeaker is powered by an integrated amplifier and the signal for this
is directly wired to the connector panel on the side of HATS, see Fig.2.2.
The mouth opening of Type 5128 has a removable adapter SO-0007 which allows a choice of
orifice size (30

11 mm or 42

16 mm).
On the chin of HATS there is a reference microphone holder which positions a 1/4  microphone
(for example Brüel & Kjær Type 4944) precisely at the ITU-T Mouth Reference Point (MRP),
25 mm from the equivalent lip plane. It can also position the microphone at the opening of the
mouth. If this holder is not required, it can either be removed by loosening the single cross-head
screw that secures it to the chin, or pushed to one side as it can rotate on this screw.
During normal use of HATS there should be no need to disassemble the mouth simulator. If
problems are experienced with the mouth simulator, contact your local Brüel & Kjær
representative.
3.1.3 Ear Simulator Construction
The construction of the artificial ear in HATS is shown in Fig.2.5. The ear consists of a removable
silicone-rubber pinna coupled to an ear canal which is terminated by an occluded ear simulator.
The ear simulator consists of a main housing which contains a number of air passages and
cavities. This design results in the main ear canal being of similar shape and volume to an average
human ear, and provides a representative acoustic impedance termination. The ear simulator can
be removed from Type 5128. If problems are experienced with the ear simulator, contact your
local Brüel & Kjær representative.
3.2 Mouth Simulator Operating Characteristics
3.2.1 Talker Frequency Response
Fig.3.2 shows the sensitivity frequency response of the mouth simulator of Type 5128 measured
at MRP, 25 mm from the lip plane, with the standard mouth insert in place.
The individually measured talker frequency response is given in the TFR file on the data disk, and
is on the calibration chart supplied with Type 5128.