OPTICOM ECHO User manual

2-wire /
4-wire
2-wire /
4-wire
sending path
receiving path Echo caused by
acoustical coupling
at site B
Echo caused by conversion
from 4-wire to 2-wire
coupling and vice versa B
far end side
A
near end side
IN
(electrical or
acoustical)
OUT
(electrical or
acoustical)
Sidetone -
Echo which is supposed
to improve the talking quality
Network
OPTICOM Product Line:
Voice/Audio Quality
PESQ ITU-T P.862
3SQM ITU-T P.563
PSQM ITU-T P.861
ECHO
PEAQ ITU-T BS.1387
Video Quality
PEVQ
Network Quality
VQmon
Voice
Quality Testing
Advanced Perceptual
ECHO Measurement Tool
OPTICOM’s Advanced ECHO measurement tool
provides accurate and repeatable estimates of
multiple audio signal echoes in a telephony net-
work. Each detected echo is characterized by an
Echo Return Loss (ERL) and its echo delay plus it
is tested whether each echo is likely to be per-
ceived as acceptable or annoying by a customer.
The ERLs and the echo delays are measured by
analyzing audio signals sent (reference audio
signal) to and received (echo audio signal) from a
network.
The Advanced ECHO measurement technology is
the latest out of OPTICOM’s family of products
for network quality assessment tools. Compared
to other echo measurement algorithms OPTI-
COM’s approach is unique because it uses real
voice signals for the measurement rather than
e.g. sine tones. OPTICOM’s ECHO tool can be
widley used in active testing in both lab environ-
ments and in network test equipment.
OPTICOM’s Advanced ECHO algorithm deter-
mines the echoes with the help of long term cor-
relations of the speech signals at a voice net-
work’s input and output (see figure above). One
advantage of using real voice signals over ordi-
nary sine tones – as other algorithms propose –
is that a voice signal is closer to the real world
telephony situation. Sine tones might be treated
more or less rigid by a network compared to real
voice signals. For example echo cancellation
devices employed in the network might be able
to easily filter out detected sine tones but they
might have difficulties handling a complex voice
like signal. Using real speech signals for the
measurement becomes even more valuable in
digital e.g. VoIP networks, where signal delays
increase due to the additional requirement for
signal processing and without active echo can-
cellation methods or suppressors the echo signal
would return to the talker annoyingly unattenuat-
ed. Another advantageous side effect is that
through the speech signal’s natural modulation a
best match of the two correlated signals can be
found with higher accuracy than with sine tones.
Therefore the results become more robust
against clipping and noise.
Key Features:
• Echo Return Loss (ERL)
and echo delays
• OEM product available as
DLL/Library optimized in
performance and memory
requirements
• Detailed statistics of the
occurrence of echoes for
e.g. comprehensive graph-
ical display and further
analysis
• Robust measurements
even if the echoes are
heavily distorted
• Multiple echo detection
Principle
PEVQ™, 3SQM™ and the OPTICOM logo are registered trademarks of OPTICOM GmbH; the ‘single-sided speech quality measure’ and
‘the perceptual quality experts’ are trademarks of OPTICOM GmbH. This information may be subject to change.
All brand and product names are trademarks and/or registered trademarks of their respective owners.
All rights reserved. Copyright © 2005 OPTICOM GmbH – www.opticom.de

Specifications
Functionality
• Echo Return Loss (ERL); echo attenuation in
dB
• ERLs and echo delays for multiple echoes
• Perceptual estimation of echo annoyance,
using subjective analysis results as stated in
ITU-T G.131
• Additional measurement outputs for compre-
hensive analysis
• Narrowband and Wideband operation
• Real speech signals for analysis
Input
• Two audio signals required:
Reference speech signal and echo signal
• 16 bit linear audio sampled at
8kHz and 16kHz
• 6 to 20 seconds in length
Output
• ERL / Delay for multiple echoes
• Statistical information of the echo analysis,
e.g. ERL / Delay histogram
• Comprehensive evaluation of the echoes
influence on conversationally perceived
quality
Platform
• Windows
• Linux
Advanced Perceptual ECHO Measurement Tool
PEVQ™, 3SQM™ and the OPTICOM logo are registered trademarks of OPTICOM GmbH; the ‘single-sided speech quality measure’ and
‘the perceptual quality experts’ are trademarks of OPTICOM GmbH. This information may be subject to change.
All brand and product names are trademarks and/or registered trademarks of their respective owners.
All rights reserved. Copyright © 2005 OPTICOM GmbH – www.opticom.de
About OPTICOM
With PSQM, PESQ and PEAQ,
OPTICOM GmbH, the pioneer
in perceptual quality testing
has been providing three
international world-class
standards for voice and audio
quality measurement since
its foundation in 1995. With
their new single-sided
speech quality measure
3SQM™, a joint development
with partners, the perceptual
experts from Germany now
presented their fourth ITU
standard. At its 10th anniver-
sary, the presentation of the
new PEVQ™ video measure
leverages the company’s
huge experience towards the
multimedia testing domain.
Recognized an industry refer-
ence, OPTICOM’s OPERA
voice/audio quality test tools
are available to users world
wide. And while specialized
on OEM customers in particu-
lar, the directory of OEM
licensees today reads like the
‘Who-is-Who’ of the
Telecoms industry. OPTICOM
is a privately held company
located in Erlangen, Germany.
Sales Contacts:
OPTICOM GmbH
Nägelsbachstraße 38
91052 Erlangen, GERMANY
Phone: [phone]
Fax: [phone]
[email protected]
www.opticom.de
North America:
Telchemy Inc.
Phone [phone]
JDSU - Acterna U.S.
Phone [phone]
Europe, Latin America,
Middle East & Africa,
Asia Pacific, CIS Countries:
JDSU - Acterna
Germany GmbH
Phone: [phone]
Through our distributor net-
work, we are represented in
more than 80 countries. To find
your local sales office, please
contact [email protected]
The diagram below gives you an example of the
results of a typical measurement with OPTI-
COM’s ECHO tool after the data was evaluated
with a spread-sheet program. The diagram is
divided into two distinct areas separated by an
extrapolated and approximated talker echo toler-
ance curve derived from the ITU-T standard
G.131. All echoes (peaks) that do not reach out of
the blue area are generally likely to be perceived
as annoying while all peaks that reach into the
orange area are sufficiently attenuated and are
tolerable – if perceived at all. Here, easily three
echo peaks can be identified which lie in the blue
area of the diagram. These echoes are too loud
to be negligible and are very likely to be per-
ceived as annoying by a customer.
0
10
20
30
40
0 80 100 240 320 400 480 500 640
ERL in dB
Delay in ms
50
Unacceptable Echo Area
ERL vs. Delay
Acceptable Echo Area
Tolerance Curve