Acoustic echo is a common phenomenon that is encountered in many types of phone calls. It occurs when speaker output is fed back to the microphone input. This will disturb the far end speaker as they hear their own voice but delayed. Acoustic echo cancellers (AEC) are used in phones or in the network to minimize this distortion. Acoustic echo, unlike line echo, is dynamic during a call as people and speakers move about.
GL's Automated Acoustic Echo Cancellation (AEC) Compliance Test Software (PKB081) is a feature rich application used to perform acoustic echo cancellation testing in accordance with ITU-T Specifications, G.167 (03/1993) and P.340 (05/2000).
The Automated AEC Test Software uses GL Communications' T1/E1 Analyzer products and the customers AEC hardware or software to perform Acoustic Echo Canceller testing. Rin and Sin files (stimulus and echo) are prepared by Automated AEC Test software in accordance with user inputs. Rout and Sout are captured and processed.
Theory of operation
The module, which includes AEC, Rin, Rout, Sin and Sout, can be a Sound Card, a Mobile Phone, a Regular Phone, an IP Phone, or a Speaker Phone. Rin is the source signal (from the far end), which goes through Acoustic Echo Canceller (AEC) and Sout is the echo cancelled signal, which comes out of AEC. The leakage from Rout to Sin is due to the acoustic echo.
In the past, modeling and replicating acoustic echo has been quite complicated often requiring a sound chamber, head and torso, etc. GL has simplified the process considerably by modeling the acoustic echo path and dynamically changing its characteristics. In effect, the echo path can be made to vary in a manner similar to the real world. Also, the echo path can be specified to mimic a "small room", a "car", a "medium size conference room", etc. Dynamism is introduced by slowly morphing the impulse response coefficients in a predetermined manner.
The above features have been incorporated into DSP operators within our Windows Client Server (WCS) software. This software is available with our T1 E1 product platforms, including USB T1 E1 Analyzer, Universal T1 E1 Cards, and
tProbe™ T1 E1 units. GL's T1 E1 Analyzer cards is featured with the Windows Client/Server DSP Operation module, which allows real-time testing using DSP commands to perform functions such as Amplification/Attenuation, Delay, Filter, File Tx/Rx, Logical operations, Echo Cancel, and so on.
Our DSP Operators in Windows Client Server (WCS) software offers following capabilities:
- Simulate acoustic echo into a mobile phone
- Generate dynamic (changing) acoustic echo
- Test acoustic echo cancellers in mobile phones and other signal processing devices
For comprehensive information, please visit Dynamic DSP Operation web page.
Automated Acoustic Echo Cancellation (AEC) test software works in conjunction with our T1 E1 product platforms, including USB T1 E1 Analyzer, Universal T1 E1 Cards, and tProbe™ T1 E1 units. Automated AEC Test Software performs a full analysis (with detailed displays) that results in a "Pass" or "Fail". Automated AEC testing concepts are implemented within the software for various End to End Applications (Mobile, TDM, and VoIP) scenarios.