Noise is everywhere and in most applications that are related to audio
and speech, such as human-machine interfaces, hands-free communications,
voice over IP (VoIP), hearing aids,
teleconferencing/telepresence/telecollaboration systems, and so many
others, the signal of interest (usually speech) that is picked up by a
microphone is generally contaminated by noise. As a result, the
microphone signal has to be cleaned up with digital signal processing
tools before it is stored, analyzed, transmitted, or played out. This
cleaning process is often called noise reduction and this topic has
attracted a considerable amount of research and engineering attention
for several decades. One of the objectives of this book is to present in
a common framework an overview of the state of the art of noise
reduction algorithms in the single-channel (one microphone) case. The
focus is on the most useful approaches, i.e., filtering techniques (in
different domains) and spectral enhancement methods. The other objective
of Noise Reduction in Speech Processing is to derive all these
well-known techniques in a rigorous way and prove many fundamental and
intuitive results often taken for granted. This book is especially
written for graduate students and research engineers who work on noise
reduction for speech and audio applications and want to understand the
subtle mechanisms behind each approach. Many new and interesting
concepts are presented in this text that we hope the readers will find
useful and inspiring.
