The Removal of Acoustic Echo
Autore
Federico Brucciani - Università degli Studi di Pisa - [1998-99]
Documenti
Abstract
Echo in a Loudspeaker Enclosure Microphone (L.E.M.) System is generally undesirable but inevitable. There are two possible source of echo in a L.E.M. system. The impedance mismatch in hybrids generates network echo. The acoustic coupling between loudspeaker and microphone produces acoustic echo. Echo cancelers are used to control these echoes.
In this thesis, we analyze the Least Mean Square ( L.M.S.) and the Normalized Least Mean Square ( N.L.M.S.) and evaluate their performance as acoustic echo cancellers. The algorithms are compared based on their convergence rate, echo return loss ( E.R.L.) and complexity of implementation. While L.M.S. is simple , its convergence rate is dependent on the eigenvalue spread of the signal. In particular, it converges slowly with speech as input. This problem is mitigated in N.L.M.S. . The complexity of N.L.M.S. is comparable to that of L.M.S..
In this thesis, we analyze the Least Mean Square ( L.M.S.) and the Normalized Least Mean Square ( N.L.M.S.) and evaluate their performance as acoustic echo cancellers. The algorithms are compared based on their convergence rate, echo return loss ( E.R.L.) and complexity of implementation. While L.M.S. is simple , its convergence rate is dependent on the eigenvalue spread of the signal. In particular, it converges slowly with speech as input. This problem is mitigated in N.L.M.S. . The complexity of N.L.M.S. is comparable to that of L.M.S..
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