BRUEL & KJAER 4128-C - Page 36

HATS Type 4128-C, Handset Positioner Type 4606 – User Manual30
Fig.2.9
Off-axis response of Type
4128-C (180) in the
free-field (20 Hz – 20kHz)
Fig.2.10
Off-axis response of Type
4128-C (270) in the
free-field (20 Hz – 20kHz)
2.3.1 Closed-volume Characteristics of the Ear Simulator
The Right Ear Simulator Type 4158-C delivered with the HATS is equivalent to Brüel &Kjær
Type 4157, but is usually used open, instead of with coupling devices. Nevertheless, the
closed-volume characteristics of the ear simulator may be of interest and so are included here
reprinted from the Type 4157 instruction manual.
Transfer Impedance
The transfer impedance was measured using a special adaptor DP-0276, which allows a l/4
condenser microphone Type 4938 to be attached to Type 4157 and used as a sender
microphone. The measurements are made 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.
-20
-15
-10
-5
5
10
15
20
200
2k
20k
dB
Angle of incidence = 180
o
20
990230
Frequency (Hz)
0
-20
-15
-10
-5
5
10
15
20
200
2k
20k
dB
Angle of incidence = 270
o
20
990231
Frequency (Hz)
0