HATS Type 4128-C, Handset Positioner Type 4606 – User Manual28
particular model, and this measurement can also be found in file LFR_R on the calibration CD.
A similar measurement for the left ear can be found in file LFR_L on the CD supplied with
Left Ear Simulator Type 4159-C.
Fig.2.6 Typical Listener free-field (LFR) and diffuse-field (DFR) curves for HATS (20Hz – 20 kHz)
If measurements are to be made using both ears at the same time, then the matching between
the left and right ears of Type 4128-C will be a combination of the tolerances on the pinnae (as
given in the specifications), and the tolerances on the ear simulators fitted, as given in the
IEC 60318–4 standard with which the ear simulators comply. Using the individual LFR
measurements supplied on CD with Types 4158-C and 4159-C, mismatch can be corrected for
using the post-processing facilities of an analyzer like Brüel& Kjær PULSE Audio Analyzer.
If left- and right-ear measurements are not needed simultaneously, the possible mismatch can
be reduced to that due to pinna differences by using only one ear simulator; the ear simulator is
easily transferred from one ear to the other.
The variation between any two left pinnae or any two right pinnae is less than 1 dB, so if
replacement pinnae are used there will be no problem comparing results with those of previous
measurements. For optimum accuracy the pinna marked with the serial number of Type 4158C
(i.e. that which is part of Type 4158-C) should be used, as it is with this pinna that the
calibration of Type 4158-C is made. The same applies to Type 4159-C.
Listener Diffuse-field Frequency Response
The Listener Diffuse-field Frequency Response (i.e., the overall frequency response from the
undisturbed diffuse-field to the eardrum of the simulated listener) is shown in Fig.2.6. The
measurement is stored on the calibration CD in file DFR.
-20
-15
-10
-5
0
5
10
15
20
200
2k
20k
Frequency (Hz)
dB
Diffuse field frequency response (DFR)
Listener free field frequency response (LFR)
20
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