文档介绍：Impedance of Real and Artificial Ears
PARTI: Investigations of a New Insert Earphone Coupler 3
(Small Artificial Ear)
Authors: Per V. Briiel
Erling Frederiksen
Hilmer Mathiasen
Gunnar Rasmussen
Erik Sigh
PART II: Impedance Measurements of Volumes 30
Authors: Per V. Bruel
Viggo Tarnow
PART III: Applications of Small Artificial Ears 33
Authors: Per V. Bruel
Erik Sigh
PART I
For helping the hearing aid industry and the users of hearing aids, IEC has described in
R 1261> — 1961 — an artificial ear called the IEC 2 cm3 Coupler, which could be used
for evaluation of sensitivity and frequency response of hearing aid earphones. A sketch
of the coupler is shown in Fig. 1, top left.
Fig. 1. Cross-section and dimensions of the IEC 2 cm3 coupler, the Zwislocki, Diestel-
P. . and the Keller coupler
The coupler consists of a 2 cm3 volume which should simulate the volume between
the tip of the ear mould and the eardrum, including the elasticity of the eardrum and
the inner part of the ear canal.
An 1 8 mm long and 3 mm diameter cylindrical cavity leads from the earphone under
test to the volume. This cavity simulates the tubular portion of an average ear mould.
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The whole ear device was suggested already in 1 949 and described in an ASA stand­
ard . The coupler in the present configuration is therefore rather old, and it is
now known that both the impedance and the frequency response differ considerably
from those of the human ear.
Many investigators have looked into the problem of making a new coupler, for example,
Zwislocki2), Diestel3) and Keller 4) together with others e up with suggestions
for revised versions of couplers for insert earphones shown in Fig. 1. These attempts
will only be briefly touched upon here.
Requirements
By coupler is normally understood a device which connects the earphone under test to
a microphone in such a way that the working load on the earphone is the