He added, “A voice call may transit a variety of networks – Mobile, VoIP, TDM, and others. A typical call can have many of the following characteristics that can affect quality: narrowband (8 kbps) or wideband call (> 64 kbps), end-to-end digital but with D/D conversions (codec conversions), many D/A and A/D conversions, additive noise and/or background noise, speech level variations, variable delay, echo in the form of sidetone, line echo, or acoustic echo, signaling and voiceband conversions that affect DTMF, FAX, and MODEM transmissions,packet delay, loss, sequencing, and duplications”.
Mr. Bichefsky explained, “To provide a comprehensive assessment of voice quality irrespective of network type, GL has combined various tools together into one platform consisting of VQuad, Dual UTA, USB T1 E1, and WEBViewer. This platform provides the ability to make VoIP, TDM, and Mobile calls from any fixed or mobile location. All interface flexibility is provided (2Wire, 4Wire, VoIP, TDM, and Mobile) within the Dual UTA and USB T1 E1 Analyzer. In addition, VQuad provides algorithms for signaling, voice transmission, and voice quality assessment. WEBViewer provides the central point where voice metrics are stored and displayed through a WEB interface”.
“Recently, GL introduced Echo Measurement Utility (EMU) software within this architecture to assess sidetone, line, and acoustic echo and corresponding delays. EMU is an offline adjunct analysis application (under control of VQuad) that compares the source and received files to determine echoes and delay of echoes. The EMU provides delay and ERL measurements for all detected echoes, along with an ‘ERL vs Delay’ plot where each echo is depicted within the plot. One can zoom-in on a particular echo to gauge overall echo impairments. In addition, the application includes signal graphs for source signal, received signal, error signal, and adaptive filter coefficients”.
* Measures EPD in msec and ERL in dB
* Compares source and received files to determine maximum of 4 echoes
* Ability to automate the entire test process using VQuad™ scripting including sending the results to the central database for access via GL’s WebViewer™
* Detailed offline analysis
* Supports Line and Acoustic Echo Modes
* Graphically displays source signal, received signal, error signal, and adaptive filter coefficients
* Allows zoom-in on each graph, and exporting snapshot of these graphs to a file for later analysis
* Calculates adaptive filter coefficients and echo characteristics for the error signal
* Speaker option to play the audio files (intrusive and non-intrusive)
* Option to zoom-in on any particular echo to investigate further