Preamplifiers
With the 43AE, the externally polarized RA0045 is delivered with a standard preamplifier, e.g. a
26AC ¼” Preamplifier fitted with an adapter.
With the 43AE-S1 the prepolarized RA0045-S1 is delivered with the 26CB ¼” Preamplifier
fitted with an adapter.
Characteristics
The acoustic input impedance of the RA0045 closely resembles that of the human ear and, as a
result, loads a sound source in very much the same way.
It can be used with:
Low-leak Pinna Simulator Type RA0056.
High-leak Pinna Simulator Type RA0057
in accordance with ITU-T Recommendation P.57 (08/96) “Series P: Telephone transmission qual-
ity, Objective measuring apparatus: Artificial ears ”, Type 3.1-3.4.
The RA0045 embodies a number of carefully designed volumes connected via well-defined and
precisely tuned resistive grooves. In an equivalent electrical circuit, capacitors would represent the
volumes, and inductance and resistance would represent respectively air mass and air flow within
the resistive groves. Fig. 10 shows a typical coupler frequency response of the RA0045.
Fig. 10.
Type RA0045 - typical coupler frequency response re. 500 Hz
The input impedance is measured using a special impedance probe as described in ITU-T Recom-
mendations P.57 (08/96). This measures the impedance of the RA0045 as seen from the Ear
Reference Point (ERP). The impedance is defined as the ratio of the sound pressure at the ERP
to the corresponding particle velocity. The sound pressure is measured with a probe microphone
while a constant particle velocity is maintained via a high acoustic impedance sound source.
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LI0070 – 28 June 2017
