GRAS RA0039 User manual

Instruction Manual
RA0039 Ear Simulator IEC 60318-1
www.gras.dk
LI0074 – 28 September 2017

Revision History
Revision Date Description
1 28 September 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
Characteristics ........................................................................................... 5
Warranty, Service and Repair ........................................................... 6
Calibration................................................................................................. 6
Warranty................................................................................................... 6
Service and Repairs.................................................................................... 6
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Introduction
The RA0039 IEC 318 Ear Simulator uses a ½” microphone, e.g. the G.R.A.S. 40AG. The artifi-
cial ear complies with the following international requirements:
IEC 60318 Electroacoustics – Simulators of human head and ear - Part 1: Ear simulator for
the calibration of supra-aural earphones.
ITU-T Recommendations P.57 Series P: Telephone transmission quality, Objective measur-
ing apparatus: Artificial ears.
It is also part of the 43AA and 43AD Ear Simulator Kits.
Components
The RA0039 comprises the following user-serviceable components:
GR0335 Body of Artificial Ear
GR0338 Removable Ring
GR0402 Removable Ring
GR0606 Guard Ring
GR0606 is a substitute for the normal protection grid of the 40AG Microphone if requirements
call for a LS2aP microphone. Note: this will leave the diaphragm of the microphone exposed!
The RA0039 is delivered as shown in Fig. 1a. An exploded view of its user-serviceable compo-
nents is shown in Fig. 1b.
It uses a ½” pressure microphone such as the G.R.A.S. 40AG with a 26AK ½” Preamplifier or
¼” Preamplifier 26AC fitted with RA0001 Adapter. If ordered with a microphone, the RA0039
will be calibrated with the specific microphone and delivered with the resulting calibration chart.
Fig. 1. a) RA0039 Ear Simulator as delivered b) Exploded view of all the user-serviceable components of the RA0039
GR0338
Removable
ring
GR0402
Removable
ring
GR0335
Body of
Ear Simulator
a) b)
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Characteristics
The acoustic input impedance of the RA0039 closely resembles that of the human ear and, as a
result, loads a sound source in very much the same way.
The RA0039 embodies a number of carefully designed volumes connected via well-defined and
precisely tuned capillary tubes. In an equivalent electrical circuit (see Fig. 2), capacitors would
represent the volumes, and inductance and resistance would represent respectively air mass
and air flow within the capillary tubes. The input impedance (see Fig. 3) is measured using a
special impedance probe as described in ITU-T Recommendations P.57 (08/96). This measures
the impedance of the RA0039 as seen from the Ear Reference Point (ERP). The impedance is
defined as the ratio of the sound pressure at the ERP to the corresponding particle velocity. The
sound pressure is measured with a probe microphone while a constant particle velocity is main-
tained via a high acoustic impedance sound source.
Fig. 2. RA0039 lumped parameter model
The absolute sensitivity of the RA0039 at 1kHz is given both as the Open Ear Sensitivity and the
Closed Ear Sensitivity. The Open Ear Sensitivity is the ratio of the output signal from the pream-
plifier to the input pressure signal at the ERP with open coupler. The Closed Ear Sensitivity is the
ratio of the output signal from the preamplifier to the input pressure signal at the ERP with closed
coupler.
Fig. 3. RA0039 acoustic input impedance Fig. 4. RA0039 closed-coupler frequency response
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Warranty, Service and Repair
Calibration
Before leaving the factory, all G.R.A.S. products are calibrated in a controlled laboratory environ-
ment using traceable calibration equipment.
We recommend a yearly recalibration at minimum, depending on the use, measurement environ-
ment, and internal quality control programs.
We recommend calibration prior to each use to ensure the accuracy of your measurements.
Warranty
Damaged diaphragms in microphones can be replaced. The microphone diaphragm, body, and
improved protection grid are made of high-grade stainless steel, which makes the microphone
resistant to physical damage, as well as corrosion caused by aggressive air or gasses. This,
combined with the reinforced gold-plated microphone terminal which guarantees a highly reli-
able connection,enables G.R.A.S. to offer 5 years warranty against defective materials and
workmanship.
The warranty does not cover products that are damaged due to negligent use, an incorrect power
supply, or an incorrect connection to the equipment.
Service and Repairs
All repairs are made at G.R.A.S. International Support Center located in Denmark. Our Support
Center is equipped with the newest test equipment and staffed with dedicated and highly skilled
engineers. Upon request, we make cost estimates based on fixed repair categories. If a product
covered by warranty is sent for service, it is repaired free of charge, unless the damage is the
result of negligent use or other violations of the warranty. All repairs are delivered with a service
report, as well as an updated calibration chart.
WEEE directive:
2002/96/EC
CE marking directive:
93/68/EEC
Manufactured to conform with:
RoHS directive:
2002/95/EC
G.R.A.S. Sound & Vibration continually strives to improve the quality of our products for our
customers; therefore, the specifications and accessories are subject to change.
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