Advanced Perceptual
ECHO Measurement Tool

OPTICOM’s Advanced ECHO measurement tool provides accurate and repeatable estimates of multiple audio signal echoes in a telephony network. 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 perceived 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 OPTICOM’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 environments and in network test equipment.

> Principle
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> 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 graphical display and further analysis
Robust measurements even if the echoes are heavily distorted
Multiple echo detection
OPTICOM’s Advanced ECHO algorithm determines the echoes with the help of long term correlations of the speech signals at a voice network’s input and output (see figure above). One advantage of using real voice signals over ordinary 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 cancellation methods or suppressors the echo signal would return to the talker annoyingly unattenuated. 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.

The diagram below gives you an example of the results of a typical measurement with OPTICOM’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 tolerance 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 perceived as annoying by a customer.

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> Specifications Advanced Perceptual ECHO Measurement Tool
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 comprehensive analysis
  Narrowband and Wideband operation
  Real speech signals for analysis
Input data 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
> Download more detailed Technical Specifications

Download OPTICOM’s Advanced ECHO Measurement Tool
[as PDF / 162 kb ]