Some Typical Examples Of Coupler Adaptation - BRUEL & KJAER 4152 Instructions And Applications
Artificial ear 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.
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combined with th
e
B
&
K Level Recorder T yp
e
2305 the m easuring arrange-
m ent can now
automa
ti
cally
r ecord
the
h
a rmonics
of
the device
under test
on
frequency
calibrated
pa
per.
A
very common
use
of
this
combination is in
the
tes ting
of
freuency
ch ar acteristics with
a ssocia
ted h armoni cs produced
in
earphones.
A
m
easuring
set-up
suitable
for this
purpose is
sketched in
F ig.
3.1.
DODDOODOD
OD
OOQODOOODOODDQDOOOODODDODoaOOOOOOODDOOO
----
Measuring Of
" ..
fundamentgl
CI ..
in egrl}hooe
·2nd.
harm.'
3nd.
harm.
100
1000
Fundamental
-
Noise Level
",
_ " ,
e
u.,.
10000
1,,1(2111
)'"
c u..,
-163751"
Fig.
9.2.
Typical recording of frequency characteristics ("Fundamental") Wld
harmonic signals
in
earphones.
In Fig. 3.2 are given the recorded results of measuring the fundamental
together with the harmonics produced in an earphone measured by setting
the filter switch on the Spectrometer so that it runs ahead of the frequency
scanning of the BFO, the selected space difference being in accordance with
the harmonic which is going to be measured. By means of the facility
included in the Level Recorder Type 23(}5, which allows
the
recording paper
to be reversed by one chart length without loosing the synchronization
between the BFO and
the
Spectrometer, the harmonics are readily recorded
on the same chart as the fundamental.
Some Typeical Examples of Coupler Adaptation.
As mentioned previously the ear mould
substitute
of the normal 2 cm
3
coupler may be
repla
ced by special
arrangements. Figs.
3.3 to 3.6 show some
typical
examples
of thi
s k ind
of
a
dap
tatio
n
.
Fig. 3.3 makes use of the ear mould substitute such as is used for the
measurement of hearing aids with coupling pieces. The hearing aid shown is
of the type fitted into spectacle frames
.
In Fig. 3.4 the rubber seal is replaced by a special fitting for measurements
on hearing aids when the coupling pieces are
removed.
When hearing aid coupling pieces are provided with ear inserts an arrange·
ment as shown in
Fig. 3.5,
may be used for the measurement.
17
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