Gannamaneni Geetha Chowdary , pp. 73. ING/School of Engineering, 2012.
The whole dimension of communications has been changed by the rapid
growth of technology. Today people are more interested in hands-free com-mucation, which makes use of loud speaker and high gain microphone, in
place of the old modeled wired telephone. The main advantage of wireless
system is that, more than one person can participate in conversation while
freely moving in the room. The presence of large acoustic coupling between
speaker and microphone would produce a loud acoustic echo making the con-versation difficult.
The term Acoustic Echo Cancellation (AEC) refers to a process of
removing echo from the received signal that contains one or more delayed
signals (copies of the original signal). The primary step while cancelling an
echo is to identify the transmitted signal which reappears with some delay.
Once the echo is identified it is cancelled by subtracting from transmitted
signal. Echo cancellation can be done using either echo suppressors or echo
cancellers, or in some case both. But suppressors support only half duplex
communication leading to the invention of echo cancellers which allows both
the speakers to talk at the same time.
The main objective of this research is to model a room and cancel the
acoustic echo being generated by a speaker and microphone. This
dissertation provides a comparison of LMS, NLMS, LLMS and RLS
adaptive algorithms in terms of echo return loss enhancement ( ERLE) value
and provides the best suitable algorithm for usage in adaptive filters for
AEC. AEC is simulated and results are evaluated by using Matlab