6.2.11. Sound
Level
Calibrator 4230
This
is
a pocket sized, portable,
battery driven instrument weighing
only
260 gm.
It
produces 94 dB
re
2 x
10-
5
N/m
2
± 0.25 dB at
1000Hz
± 1.5% which
makes
it
independent
of
weighting networks. Its waveform
is
sinusoidal and
has
less
than
1%
distor-
tion
. The sound pressure
is
independ-
ent
of
microphone volume and static
pressure.
It
fits one inch
and
half inch
microphones.
6.2. 12.
Accelerometer Calibrator 4291
The 4291
is
a portable calibrator
for
vibration measurements which
can
be
operated either
from
internal
batteries
or
from
an
external 28
Volt
DC supply.
It
produces a calibration
level
of
1 g peak
with
accuracy better
than
2%
at a frequency
of
80
Hz.
Its
use
with
the 2209
is
described in
section 3.3.1.
6.2.13.
Artificial
Ears
4152/53
Fig.6.26.
4230
!
A=w
Tl"PP'
<42.91
Fig.6.27. 4291
Artificial
Ears
Type 4152 and 4153 were designed
to
enable electro-
acoustical
measurements on earphones
to
be
made under well-defined
acoustical
conditions. Type 4152
is
used
with
couplers which
fulfil
there-
quirements
of
IEC R 126, ANSI
Z.
24.5-
1951 and ANSI
Z.
24.9-
1949.
It
consists basically
of
a replaceable acoustical coupler
and
two
sockets; ( i)
for
the mounting
of
a Condenser Microphone Cartridge Type 4144
with
(ii)
a Microphone
Preamplifier Type 2619
or
the Impulse Precision Sound Level
Meter Type 2209.
Type 4153
was
built
in conjunction
with
working group
WG
11
of
the
I
EC
technical committee TC 29, on the standardization
of
an
improved
artificial
ear
for
calibration purposes.
86
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