| P.340, P.501, P.502, P.581, VDA
Specification for Car Hands-free Terminals |
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HQS-HFT (Code 6764-6767)
HEAD acoustics Quality Standard,
Digital Hands-Free |
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VDA-HFT (Code 6770)
VDA-Specification,
Car Hands-free Terminals |
| read more |
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ACQUA (Code
6810)
Communication Analysis System |
| read more |
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MFE VI.1 (Code 6462)
mit
Analog USB Front End with Level Adjustment
and Integrated Mouth Amplifier |
| read more |
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HMS II.3 (Code 1230)
Artificial Head Measurement System with
Ear Simulator and Mouth Simulator |
| read more |
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HIS L (Code 1231)
Impedance simulation - left ear |
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HAE-car (Code 6970)
Automated Equalization for Background
Noise Simulation in Car Cabins |
| read more |
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3 x PEQ V
Programmable, digital Equalizer |
| read more |
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3 External Power Amplifiers |
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4 Loudspeakers |
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1 Subwoofer |
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Radio Tester, e.g.
CMU 200 |
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| Hands-free terminals require a
specific methodology to evaluate their transfer characteristics.
Standard parameters such as loudness ratings, frequency responses,
terminal coupling loss etc. cannot be used to determine the
subjectively relevant speech quality parameters. |
| The speech quality of hands-free
terminals is mainly determined by parameters such as double
talk performance, quality of background noise transmission,
switching and echocanceling characteristics. These parameters
were determined in listening tests. To allow an objective evaluation
of these parameters, new test signals and test procedures were
developed by HEAD acoustics. |
| In order to evaluate the double
talk performance of hands-free terminals a special test sequence
is available. This test sequence consists of specially combined
composite source signals CSS (according to ITU-T Rec. P. 501),
which activates the sending and receiving direction under various
conditions. A special test configuration is available for the
HEAD acoustics Communication
Analysis System ACQUA. |
| For the evaluation of switching
times various test stimuli are used: CSS, voiced sounds, artificial
voice (ITU-T P. 50). A variety of test setups have been composed
and are available for ACQUA.
These test setups allow the determination of all switching characteristics
of a hands-free phone under various conditions. A description
of the subjectively relevant parameters for switching characteristics
is included in the test suite. |
| The background noise transmission
quality can be evaluated by a special measurement setup including
a variety of background noises. For example, the HEAD acoustics
products HAE-car
(for car cabins) and HAE-BGN
(for test laboratories) allow an easy realization of these scenarios.
For the examination of any kind of time variant behavior under
various conditions special measurement procedures have been
created. They include a variety of test signals such as variations
of the CSS, artificial voice etc. and are available for ACQUA.
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| For the examination of the quality
parameters of acoustics echo cancellers special measurement
procedures have been developed. The tests are based on the principles
described in ITU-T Rec. G.167. However, much more detailed tests
have been added. |
| Of course, besides all these measurements,
all known measurement parameters and test suites have been implemented,
as described e.g. in ITU-T Recommendation P.340, ETSI ETS 300-245
part 3 (IEEE P 1329 in preparation). Moreover, in co-operation
with HEAD acoustics the Association of German Automobile Manufacturers
(VDA, "Verband der deutschen Automobilindustrie") has developed
a specification for the measurement of car hands-free terminals,
which is also available as ACQUA
test suite. |
| Version 1.5 of the VDA specification
for car hands-free terminals is now available as measurement
standard VDA-HFT for ACQUA.
The new version now also supports the objective speech quality
assessment of hands-free terminals using TOSQA2001. |
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Hands-Free
Telephony (Car)
