G.R.A.S. 43AE User manual

Instruction Manual
43AE Ear Simulator Kit According to ITU-T Rec. P57 Type 3.2
43AE-S1 Ear Simulator Kit According to ITU-T Rec. P57
Type 3.2, prepolarized
www.gras.dk
LI0070 – 28 June 2017

Revision History
Revision Date Description
1 28 June 2017 Extracted from Earbook as separate document
Any feedback or questions about this document are welcome at [e-mail].
Copyright Notice
© 2005-17 G.R.A.S. Sound & Vibration A/S
http://www.gras.dk
Any technical documentation that is made available by G.R.A.S. is the copyrighted work of
G.R.A.S. and is owned by G.R.A.S.
The content in this document is subject to change without notice. G.R.A.S. Sound & Vibration A/S
is not liable or responsible for any errors or inaccuracies that may appear in this document.
Trademarks
Any other product names mentioned in this document may be trademarks or registered trade-
marks of their respective companies and are hereby acknowledged.
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Contents
Introduction.................................................................................. 4
Components.............................................................................................. 4
Additional Equipment ................................................................................. 4
The 4 stages of the Test Procedure.................................................... 6
1: Setting up the Ear Simulator ................................................................... 6
2: Calibration............................................................................................. 7
3: Placing the Ear Simulator on the Earpiece/Earphone................................... 8
4: Applying the Test Signal ......................................................................... 8
Frequency Response of the 43AE .............................................................. 10
Warranty, Service and Repair......................................................... 11
Calibration............................................................................................... 11
Warranty................................................................................................. 11
Service and Repairs.................................................................................. 11
Appendix
The RA0045 Ear Simulator ........................................................... 12
Introduction ............................................................................................. 12
Components............................................................................................ 12
Level Calibration ...................................................................................... 13
Frequency Calibration of the RA0045......................................................... 15
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Introduction
The 43AE Ear Simulator Kit is for acoustically testing supra-aural 1 earphones, telephone hand-
sets and loudspeakers, and complies with the following international requirements:
ITU-T Recommendation P.57 (08/96) “Serie P: Telephone Transmission quality. Objective
measuring apparatus: Artificial ears”.
Components
43AE Ear Simulator Kit
The 43AE Ear Simulator comprises the following main components:
RA0045 IEC 60318-4 Ear Simulator with 40AG microphone included, see page 4
26AC ¼” Preamplifier
RA0001 ¼” - ½” Adapter
RA0056 Low-leak Pinna Simulator
RA0057 High-leak Pinna Simulator
43AE-S1 Ear Simulator Kit prepolarized
The 43AE-S1 uses the same componets as the 43AE except:
RA0045 IEC 60318-4 Ear Simulator with 40AO microphone included.
26CB ¼” Preamplifier
When assembled as shown in Fig. 1, it is ready for testing supra-aural earphones, telephone
handsets and loudspeakers.
26AC
¼" Preamplifier
RA0045
IEC 60318-4
Coupler
RA0001
¼" - ½” Adapter
Caution! When attach-
ing RA0001 to the
RA0045, use only
gentle finger force.
Fig. 1. Assembled 43AE Ear Simulator Kit
1An earphone applied externally to the ear
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Fig. 2 shows an exploded view of its user-serviceable components.
RA0001 Adapter
screws onto the
RA0045
Caution! When attach-
ing RA0001 to the
RA0045, use only
gentle finger force
26AC ¼" Preamplifier
(shown) or 26CB
RA0045 Ear Simulator
screws into one of the
Pinna Simulators
Simulated
ear canal
extension
Fig. 2. Exploded view of all the user-serviceable components of the 43AE Ear Simulator Kit
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Additional Equipment
The following additional equipment is required for making the necessary measurements:
1) Power supply for the 26AC,¼” Preamplifier
e.g. the G.R.A.S. 12AK Power Module.
2) Calibration-check source for the Ear Simulator, e.g. the G.R.A.S. 42AA Pistonphone which
produces 114 dB re. 20 μPa (10 Pa) at 250 Hz
3) Audio signal generator capable of generating one or more of the following within the audio
frequency range 2:
logarithmically swept tones
pink noise
This audio signal is fed (directly or indirectly) to the earphone.
4) Audio frequency analyser capable of one or both of the following:
wide band measurement
⅓ octave-band measurement
The audio analyser receives, via the 12AK, the signal picked up by the Ear Simulator, and,
depending on whether this is a swept tone or pink noise, will:
a) measure the response of the earphone to the swept tone
Or
b) measure the response of the earphone to the pink noise in terms of ⅓ octave bands
Items 3 and 4 could be combined in the same unit, e.g. a computer fitted with suitable hardware
and software for A/D and D/A conversions in order to simulate both a signal generator and an
analyser. Fig. 3 shows a block diagram of a possible set-up for making tests.
Computer with hardware
and software for simulat-
ing:
a signal generator capable
of generating logarithmi-
cally swept tones and/or
pink noise
an audio frequency analyser
capable of wide band and/
or ⅓octave band measure-
ments
Signal from generator to earphone
Output to analyser
12AK Power Module
43AE with telephone
Input from
preamplifier
Fig. 3. Block diagram of a complete set-up for making tests
2For example from 50Hz to 10 kHz
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The 4 stages of the Test Procedure
Using the telephone as a typical example, the basic stages in the test procedure are:
1) Setting up the Ear Simulator, e.g. as shown in Fig. 3
2) Calibration check using the G.R.A.S. 42AA Pistonphone with a special adapter for the 43AE
3) Placing the Ear Simulator over the earpiece of the telephone (see example in Fig. 4)
4) Applying a signal to the telephone and analysing the output from the microphone.
Depending on requirements, the signal applied to the telephone could be:
a swept tone, e.g. under laboratory conditions
pink noise, e.g. during mass production of telephones
Pink noise testing is usually quicker, and more economical, than using swept tones.
The following sections deal in more detail with each stage of the test procedure.
1: Setting up the Ear Simulator
Note: the terms generator and analyser refer to a set up which simultaneously sends the test
signal to the earphone and analyses the signal picked up by the Ear Simulator.
With the Ear Simulator assembled and everything switched on, proceed as follows:
1) 12AK Power Module
 Connect the free end of the preamplier cable to the Lemo Input socket.
Connect, via a suitable cable, the BNC Output to the input of the analyser.
Select Lin.
Select a Gain that is within the input range of the analyser.
2) Telephone
Connect the earphone of the telephone to the signal output of the generator.
3) Adjust the signal output level from the generator to lie within the normal working range of
the earphone.
Fig. 4. Place the Ear Simulator centrally over the earpiece of the telephone
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2: Calibration
Important! do not extract the microphone housed in the RA0045 Ear Simulator since this will
invalidate the factory calibration. If it ever becomes necessary to extract the microphone, use the
special tool RA0071 available from G.R.A.S.
The following procedure, using a G.R.A.S. Pistonphone, should preferably be carried out at the
following times:
a) before a rst-time use of the 43AE to establish a baseline for subsequent checks
b) thereafter at appropriate intervals to check for repeatability
The Pistonphone must be fitted with a 1” Microphone Coupler RA0023 and used with a special
Adapter RA0119 for the 43AE, both available from G.R.A.S.
1) The set up for the calibration check is shown Fig. 5.
2) Make sure that the rubber seal of the Pinna Simulator seats firmly inside the Adapter.
3) Switch the Pistonphone on.
4) Set the Gain on the 12AK to 0.
5) Set the analyser to either wide band or to the ⅓ octave band whose centre frequency is 250 Hz.
6) When conditions are stable, note the reading in millivolts.
For a microphone of nominal sensitivity (12.5mV/Pa) and a nominal Pistonphone signal of
114 dB, an approximate value for the Low-leak Pinna Simulator RA0056 is:
• 95 mV (representing a drop of ≈ 2.4 dB)
7) Repeat, if required, with the High-leak Pinna Simulator RA0057 fitted, a corresponding
approximate value is:
• 15 mV (representing a drop of ≈ 18.4 dB)
RA0023
1" Coupler
RA0119
Pistonphone Adapter
RA0056 Low-leak
Pinna Simulator
Fig. 5. Calibration-check set-up. Make sure that the rubber seal of the Pinna Simulator seats firmly inside the Piston-
phone Adapter
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LI0070 – 28 June 2017

3: Placing the Ear Simulator on the Earpiece/Earphone
In cases of production testing, this is normally taken care of automatically. Whether automatic or
manual, the Ear Simulator must be centrally placed over the earpiece/earphone being tested so
that the sound is transmitted directly into the Ear Simulator. See example in Fig. 4.
4: Applying the Test Signal
The following describes typical procedures for applying:
a) a swept signal
b) pink noise
and refers to some typical results.
In both cases, it is assumed that the generator and analyser work to produce constant-confidence
results (i.e. maintaining a constant β T product) in real time throughout the frequency range of
interest and make the measurement data available graphically and numerically.
Swept Signal
With everything set up as described above, proceed as follows:
a) set the generator to oscillator mode
b) set the analyser to at response
c) initiate a constant-level logarithmic sweep 3 on the generator.
The analyser will follow the response of the Ear Simulator to the earphone throughout the
sweep and record and display the results accordingly.
Pink noise
With everything set up as described above, proceed as follows:
a) set the generator to pink noise mode and start generating.
b) set the analyser to ⅓ octave-band mode 3 and wait until conditions are stable.
c) start the analyser.
The analyser will record the response of the Ear Simulator to the earphone for each ⅓ octave
band and record and display the results accordingly.
In both cases, curves showing the upper and lower tolerance levels for the frequency range of
interest could be superimposed on the graphical displays.
3For example from 50Hz to 10 kHz
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LI0070 – 28 June 2017

Fig. 6. Frequency response curves of the 43AE fitted with a low-leak pinna simulator re. 1kHz.
Frequency Response of the 43AE
For measurement purposes, the 43AE is a simulation of an ear drum, ear canal and pinna
4.
The diaphragm of the built-in microphone simulates the ear drum and occupies the position
known as the DRP
5. The simulated ear canal is the hole through which sound reaches the micro-
phone (see Fig. 2). The ERP
6lies at the entrance of the outer ear. It is also used as the listening
point for the handset of a telephone (see Fig. 7 and Fig. 8).
Fig. 5.6 shows the frequency response of an IEC 60711 Ear Simulator Type 43AE fitted with a
Low-leak Pinna Simulator RA0056 for both open and closed-ear conditions. At any given fre-
quency f, the corresponding difference ∆
f between the sound levels at the ERP and DRP is given
as follows:
∆
f= DRP L,f – ERP L,f
In certain cases, for example when testing telephones, ERP
L,f could be of interest since it repre-
sents the signal originating from the ear piece of a telephone, whereas the microphone buried in
the ear simulator is exposed to, and measures, DRP
L,f .
4The part of the outer ear that projects from the head
5(ear)Drum Reference Point
6Ear Reference Point
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