|Keywords:||Reglerteknik; acoustic echo cancellation; acoustic echo suppression; hybrid system; subjective listening tests; PESQ; perception; Reglerteknik; Engineering and Technology; Electrical Engineering, Electronic Engineering, Information Engineering; Control Engineering; Teknik och teknologier; Elektroteknik och elektronik; Reglerteknik; TECHNOLOGY; Information technology; Automatic control; TEKNIKVETENSKAP; Informationsteknik; Reglerteknik; Automatic Control and Communication; Examensarbete i Reglerteknik och kommunikationssystem; teknik; teknik|
|Full text PDF:||http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-2011|
The acoustic echo problem arises whenever there is acoustic coupling between a loudspeaker and a microphone, such as in a teleconference system. This problem is traditionally solved by using an acoustic echo canceler (AEC), which models the echo path with adaptive filters. Long adaptive filters are necessary for satisfactory echo cancellation, which makes AEC highly computationally complex. Recently, a low-complexity echo suppression scheme was presented, the perceptual acoustic echo suppressor (PAES). Spectral modification is used to suppress the echoes, and the complexity is reduced by incorporating perceptual theories. However, under ideal conditions AEC performs better than PAES. This thesis considers a hybrid system, which combines AEC and PAES. AEC is used to cancel low-frequency echo components, while PAES suppresses high-frequency echo components. The hybrid system is simulated and assessed, both through subjective listening tests and objective evaluations. The hybrid scheme is shown to have virtually the same perceived quality as a full-band AEC, while having a significantly lower complexity and a higher degree of robustness.