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Methods and algorithms for quality and performance evaluation of audio conferencing systems
Umeå University, Faculty of Science and Technology, Department of Physics.
2013 (English)Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
Abstract [en]

In an audio conferencing system the sound from the loudspeaker is undesirably picked up by the microphone. This introduces echoes to the system. To remove the echoes an acoustic echo canceller can be built with an adaptive filter. The problem for the echo cancellation is that the performance of the algorithm depends on the mechanical and the acoustical properties of the system.

This thesis examines different methods for determining the performance of loudspeaker equipment and speech quality in an audio conferencing system. The influence on the echo cancellation algorithm is also examined. The methods used are the perceptual evaluation of speech quality, mean opinion score, total harmonic distortion, frequency response, cumulative spectral decay and echo return loss enhancement. Also some versions of the methods were considered.

During the measurements a conclusion was made that the perceptual evaluation of speech quality was not suitable for acoustical measurements. The results also show that the frequency response and the total harmonic distortion were the methods that had the highest correlation to the subjective performance of the loudspeaker. Total harmonic distortion also had the highest correlation to the performance of the echo canceller measured with the echo return loss enhancement. Cumulative spectral decay was good for detecting resonances in the enclosure. The different methods were thus good at different things but none of them can alone predict the performance of the system.

Abstract [sv]

Vid användning av ett konferenssystem kommer ljudet från högtalaren att oönskat plockas upp av mikrofonen. Detta introducerar ekon till systemet. För att ta bort ekon kan en akustisk ekoannulerare användas. Problemet för ekoannuleraren är att utförandet av algoritmen beror på de mekaniska och akustiska egenskaperna på systemet.

Denna avhandling undersöker olika metoder för att bestämma talkvalitén och prestandan på högtalarutrustning i konferenssystem. Det undersöks även vilket inflytande prestandan har på ekoannulleringen. De metoder som undersöks i denna avhandling är perceptual evaluation of speech quality, mean opinion score, total harmonisk distortion, frekvenssvar, en sorts kumulativ spektralanalys och echo return loss enhancement. Även en del varianter av metoderna har beaktats.

Under arbetets gång drogs slutsatsen att perceptual evaluation of speech quality inte var lämplig för akustiska mätningar. Resultaten visar även att de metoder som hade högst korrelation med den subjektiva kvalitén på högtalaren var frekvenssvaret och total harmonisk distortion. Total harmonisk distortion var även högst korrelerad med prestandan på ekoannuleraren, vilket mättes med måttet echo return loss enhancement. Resultatet från den kumulativa spectralanalysen visade att metoden var bra på att detektektera resonanser i en högtalarlåda. De olika metoderna var alltså bra på att mäta olika saker, men ingen av dem kan var för sig bestämma kvalitén på systemet.

Place, publisher, year, edition, pages
2013. , 53 p.
Keyword [en]
AEC, loudspeaker performance, audio conferencing systems, PESQ, MOS, THD, ERLE, CSD
National Category
Physical Sciences Mathematics
Identifiers
URN: urn:nbn:se:umu:diva-73216OAI: oai:DiVA.org:umu-73216DiVA: diva2:630382
Subject / course
Examensarbete i teknisk fysik
Educational program
Master of Science Programme in Engineering Physics
Presentation
2013-06-05, NA 340, Naturvetarhuset, Umeå Universitet, Umeå, 13:00 (Swedish)
Supervisors
Examiners
Available from: 2013-06-19 Created: 2013-06-18 Last updated: 2013-06-19Bibliographically approved

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Methods and algorithms for quality and performance evaluation of audio conferencing systems(2352 kB)422 downloads
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