BRUEL & KJAER 4152 User guide

Artificial Ear Type 4152
For measurement on earphones as
used in hearing aids and telephone
communication systems. Provided
with couplers made in accordance
with the lEG Recommendation
126 ,
and various American and German
Standards.

Artificial Ear
Type 4152
December 1970

Contents
Page
I. Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 3
General ..... . .................................................... 3
2 em
3
Coupler ........... .. ....................................... 4
6
~m3 Coupler .................................................... 6
2. Operation
...... ....... . .. .... .................... ....... ...... . .. 9
Operation of the Artificial Ear . . ...... ...... ..... ................. 9
Operation of a Complete Arrangement for the Testing of the Earphone 10
Artificial Ear in Connection with the Precision Sound Level Meter .. 13
3. Application . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
.. 16
Automatic Recording of Harmonics in Earphones . .. . . . . . . . . . . . . . . . . . 16
Some Typical Examples of Coupler Adaptation . . . . . . . . . . . . . . . . . . . . . . 17
4. Appcndix . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 20
Influence of Vibration ............ .. . ....... .. ........ . ... ... ..... 20
Use of protecting cover in the 6 cm
3
Coupler ... ........ ..... ...... .. 22

1. Description
General.
The Artificial Ear Type 4152 is designed to enable acoustical measurements
on earphones to be carried out under well-defined acoustical conditions .
It consists basically of a replaceable acoustical coupler, and two sockets for
the mounting of a Condenser Microphone Cartridge Type 4144, and a Micro-
phone Preamplifier Type 2619 or the Sound Level Meter Type 2203.
Fig. 1.1. The Artificial Ear Type 4152.
A spring arrangement is provided to fulfil certain Standards requirements
regarding the force applied to the object under measurement. It can be
adjusted to apply a force of 200 grammes to an earphone when using the
2 cm
s
Coupler, as prescribed in the earlier American Standard ANSI Z.
3

24 .-9.-1949 ( but not in the pr ese nt 3.3-1960 ANSI Standard ), and the German
Sta
ndard DIN 45600, and when using the 6 cm
s
coupler, the force may be
a dju sted to 500 gra mm es as prescribed in ANSI Standard Z. 24.-9.-1949
Figs. 3 and 4.
Retaining
arrangement
Coupler
Adopter i
(000111)
Mi crophone
Cartridge
Coupl.r
M ic rophone
Preomplifier(2619)
Adju st able
retaini
ng
spring
support
163761
Pig . 1.2. Sectional view of the Artificial Ear and the Condenser Microphone.
Fig. 1.2 show.s a sectional view of the socket with the mounting arrangement
for the condenser microphone. The guard ring (internal shield) principle
used in the Mi c rophone Preamplifier Type 2619 is ex tended to include the
socket which keeps th e effective transmission loss of the 4152 as low as
approximately 0.1 dB.
As indi ca ting met er, the Microphone Preamp lifier Typ e 2619 and the Measur-
ing A mplifi er Typ e 2606 can be used as well as the Sound Lev el Meter T ype
2203. See Fig. 1.3.
The 2 em3 Coupler.
One of the couplers supplied with the Artificial Ear Type 4152 is a 2 cm
3
Coupler (DB 0138) which fulfils the requirement of International Standard
(I.E.C. Recommendation Publication 126). A sectional view of the Coupler
is shown in Fig . 1.4.

=:j~il~l:i.:r
'--+--(E~~) "'"-- i- _~ - -~-~I:
2606 2619
o.
4152
b.
1637+9
Fig.I.3.
a) The Artificial Ear Type 4152, MiCl'ophone Preamplifier Type 2619 and the
Measuring Amplifier Type 2606.
b) The Artificial Ear and the Sound Level Meter Type 2203.
It consists of a housing, a standardized 18 mm ear mould s\lbstitute, and an
airtight screw seal. The housing is supplied with threads for mounting a
Microphone Cartridge 4144 in one end and for the screw seal in the other.
The screw seal is made airtight by means of a rubber ring, which is also used
as a lock arrangement for the nub of the earphones for hearing aids. The
18 mm ear mould substitute is made removable to allow other adapters
to be used, if required, as shown on p. 18.
When the Condenser Microphone cartridge is screwed into the coupler the
effective volume (including the equivalent volume of the cartridge) is 2 ems,
within the tolerances permitted by the standard.
To enable pressure equalization a capillary tube arrangement is included in
the coupler, as shown in Fig. 1.2 and 1.4.
If desired the couplers can also be used screwed directly onto a Condenser
Microphone as shown in Fig. 1.5. Fig. 1.5 shows also the exact dimensions

of the ear mould substitute for the convenience of the user who may wish
to make his own special substitutes.
Airtight rubber seal
O,Smm-D.020" wire to fill
capillary partially
Airtight
seal'----fJ!:=:;::::::;:==I=::;::::;;:;~1J
Standard pressure
microphone
Pressure equalisation
capillary
O,6mm-O,024"
1 59259
Fig. 1.4. The "normal" 2 cm
3 Coupler DB 0138.
The 6 cm
3
Couplers.
To enable acoustical tests to be made on headphones used in audiometers
and in telephone systems, two 6 cm
3
couplers are available for the Artificial
Ear Type 4152. One of these couplers, the one normally included in the
4152 ear, fulfils the requirements of th e N.B.S. 9A Coupler and ANSI
Z. 24.5-1951, the other being in accordance with the requirements of the
ANSI Z. 24.9-1949 Type 1 Coupler .
Sectional views of the couplers are shown in Fig. 1.6. According to the
standards the couplers should be used in connection with microphones
supplied with a front cavity . As the Microphone Cartridge Type 4144 is made
with a flat front, a Coupler Adapter Ring DB 0111 is supplied with the
couplers.
By unscrewing the normal protection cover from the microphone cartridge
and mounting the coupler adapter ring instead, measurements can be mad e
in complete agreement with the standards.
However, the openings of the couplers are big enough that, by accident
a small object might be dropped into the cavity and damage done to the
unprotected microphone diaphragm . To avoid this risk of damaging the
6

Ear mould
Condenser
Microphone
Adapter for 2 cm3 coupler '592<1
Fig. 1.5. Dimensional drawing of the 2 ems Coupler.
diaphragm it is recommended to place the microphone with its normal
protecting cover in the coupler. (See Appendix).
Both the 6 ems and 2 ems couplers may be used directly on the Artificial
Ear Type 4152, but if it should be desired to use the couplers directly on
a
microphone without the art ifici al ear, this may be done by employing the
method described in the following. The method of mounting the 2 ems
coup l er is described above, but to mount the two 6 cm
3
coupuers, the micro-
phone cartridge is screwed off the preamplifier and the stop collar YO 2340,
which is delivered with the coup l ers DB 0160 and DB 0161 but not wiih the
Artificial Ear Type 4152, is placed on top of the preamplifier so that the
preamplifier is recessed in the ring. By replacing the microphone cartr idge
on th e preamplifier th e stop collar is fixed in its position, and th e respective
coupler can be placed on the microphone as show n in Fig. 1.7 . When th e
7

Sec
ASA Type 1
=
I
I
I
Packing Washer --------;,~
CoupLer Adapter Ring F
Stop CoLLar
I
159262
Fig. 1.6. Sectional views of the 6 cm
3 Couplers.
couplers are used directly on the microphon e it is recommended to use one
of the B & K microphone stands.
,---- Packing Washer
,--- CoupLer Adopter
Condenser
Microphone
Cartridge
6 cc CoupLer
ASA Type 1
Stop Collar
---- Preamplifier
Fig. 1.7. Sketch showing how the 6 cm
3 Couplers are
mounted directly on
the Condenser Microphone.
8

2. Operation
To carry out meas ur eme nt s by me ans of the Artificial Ear Type 4152, it must
be fitted with a Microphone Cartridge Type 4144, a Microphone Preamplifier
Type 2619 and an indicating instrument. It is possible to us e the Sound Level
Me ter Type 2203 instead of th e pr eam plifier a nd the indic ating instrument .
To ma ke th e Artificial Ear ready for use, proc eed as follows:
Operation of the Artificial Ear.
1. Unscrew the coupler and if mounted, the Coupler Adaptor Ring.
2. Screw the Microphone Cartridge Type 4144, without protection grid, to
the microphone socket.
2 ems
Coupler 6 ems Coupler
3. If it is desir ed to use an adapter
other than the standardized 18 mm
ear mould substitute, then this
should be replaced by the desired
one , see page 18 .
4. Screw the Coupler onto the micro-
phone.
NBI Take great care not to damage
the diaphragm.
3a. Screw the Coupler Adapter
Ring onto the microphone . *)
4a. Screw the Coupler to the
Coupler Socket.
5.
Mount the earphone to be tested on the top of the Artificial Ear .
6. If the spring arrangement is used, adjust the height of this arrangement
until the correct force to the earphone can be read on the scale.
Now
the Artificial Ear is ready for use, and the indi ca ting instrument and
signal to the earphone must be connected.
*) If des ir ed, the Fron t Cover DD 00 15 may be screwed onto the Co upler Adapter Rin g.
(See Appendix).