BRUEL & KJAER 4212 Instructions And Applications page 10

furthermore, be pressed against the screw seal of the spring arrangement
(see Fig. 3}. When it is desired to use a special ear mould, the adaptor may
be taken out of the couplingspiece and the ear mould inserted instead, Fig. 6b.
airtf9ht rubber seal
table top mountti?g
OS"mm
.qo~o
"w;re
tol/11
co,oillarq port:.-o/1~·
pressure
e~voltsotion
coptl/ory Q6
177m-
qoe4-"'
diameter
or
.E cm
3
COVI'ty-
/ess than .!'lmm-
0,75J!i
11
greater than 18mm -Q71'' rnotertol : tyoss
f580f.f
Fig. 6a. Sectional view of the 2 cc coupler of the artificial ear.
For hearing aid spectacles where it is not possible to separate the earphone
and the microphone, the couplingspiece and Condenser Microphone Cartridge
+
Cathode Follower are placed inside the Test Box in the test area. This
is done by unscrewing the union nut and pulling out the microphone assembly,
which can then easily be placed in the chamber. It may in certain cases be
useful to remove the cloth in the test area, whereby the spectacles and most
of the artificial ear may be placed in the sound field remote from the
measuring plane. Se also p. 22. On page 18 is described how the Test Box is
taken apart. Furthermore, facilities are provided for replacing the standardized
2 cc coupler with the standardized 6 cc coupler (ASA Type 1, Z 24.9/1949J or
the 6 cc coupler (NBS 9A
=
ASA Z 24.5/1951}. See further page 19.
8