CHAPTER 3
Characteristics
27
3.3.4 Transfer Impedance
The transfer impedance is measured by driving the simulator at its input reference plane by a
known acoustic volume velocity and then measuring the output of the ear simulator microphone.
Fig.3.11 Magnitude of the ear simulator transfer impedance times frequency relative to the value at 500 Hz
3.3.5 General Operating Characteristics
Sidetone
The mouth-ear sidetone characteristic of HATS (that is, the influence of the mouth simulator
output on the ear simulator output) is shown in Fig.3.12 for both an open and a closed ear. Open-
ear sidetone is for practical purposes identical to the airborne portion because the structure-
borne portion has been minimized by special decoupling arrangements. For the closed-ear
measurement a closed coupler is used.
It is possible to use both the ear simulator and the mouth simulator at the same time.
−10
−5
0
5
10
15
20
25
30
35
20 200 2000 20 000
dB
Frequency (Hz)
990232/1
Transfer Impedance
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