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ELSEVIER
Speech
Communication
48
(2006)
111126
www.elsevier.com/locate/specom
A
noise
reduction
system
based
on
hybrid
noise
estimation
technique
and
postfiltering
in
arbitrary
noise
environments
Junfeng
Li
*,
Masato
Akagi
School
of
Information
Science,
Japan
Advanced
Institute
of
Science
and
Technology,
11
Asahidai,
Tatsunokuchi,
Nomigun,
Ishikawa
9231292,
Japan
Received
10
August
2004;
received
in
revised
form
21
June
2005;
accepted
22
June
2005
Abstract
In
this
paper,
we
propose
a
novel
noise
reduction
system,
using
a
hybrid
noise
estimation
technique
and
postfilter
ing,
to
suppress
both
localized
noises
and
nonlocalized
noise
simultaneously
in
arbitrary
noise
environments.
To
estimate
localized
noises,
we
present
a
hybrid
noise
estimation
technique
which
combines
a
multichannel
estimation
approach
we
previously
proposed
and
a
softdecision
singlechannel
estimation
approach.
Final
estimation
accuracy
for
localized
noises
is
significantly
improved
by
incorporating
a
robust
and
accurate
speech
absence
probability
(RA
SAP)
estimator,
which
considers
the
strong
correlation
of
SAPs
between
adjacent
frequency
bins
and
consecutive
frames
and
makes
full
use
of
the
high
estimation
accuracy
of
the
multichannel
approach.
The
estimated
spectra
of
localized
noises
are
reduced
from
those
of
noisy
observations
by
spectral
subtraction.
Nonlocalized
noise
is
further
reduced
by
a
multichannel
postfilter
which
is
based
on
the
optimally
modified
logspectral
amplitude
(OMLSA)
esti
mator.
With
the
assumption
of
a
diffuse
noise
field,
we
propose
an
estimator
for
the
a
priori
SAP
based
on
the
coher
ence
characteristic
of
the
noise
field
at
spectral
subtraction
output,
high
coherence
at
low
frequencies
and
low
coherence
at
high
frequencies,
improving
the
spectral
enhancement
of
the
desired
speech
signal.
Experimental
results
demonstrates
the
effectiveness
and
superiorities
of
the
proposed
noise
estimation/reduction
methods
in
terms
of
objective
and
subjec
tive
measures
in
various
noise
conditions.
©
2005
Elsevier
B.V.
All
rights
reserved.
Keywords:
Hybrid
noise
estimation;
Postfiltering;
Coherence
function;
Speech
presence
uncertainty
1.
Introduction
Corresponding
author.
Tel.:
+81
761
51
1236;
fax:
+81
761
51
1149.
Email
addresses:
junfeng@jaist.ac.jp
(J.
Li),
akagi@jaist.
ac.jp
(M.
Akagi).
Recent
years,
noise
reduction
has
been
in
great
demand
for
an
increasing
number
of
speech
01676393/$

see
front
matter
©
2005
Elsevier
B.V.
All
rights
reserved.
doi:10.1016/j.specom.2005.06.013