Digital Signal Processing Reference
In-Depth Information
Chapter 10
REDUCTION OF DIFFUSE NOISE IN MOBILE
AND VEHICULAR APPLICATIONS
Hamid Sheikhzadeh
1
, Hamid Reza Abutalebi
2
, Robert L. Brennan
1
, and
George H. Freeman
3
1
Dspfactory Ltd., 611 Kumpf Drive, Unit 200, Waterloo, Ontario, Canada N2V 1K8,
2
Electrical Engineering Dept., University of Yazd, Yazd, Iran;
3
Electrical and Computer
Engineering Dept., University of Waterloo, 200 University Ave. West, Waterloo, Ontario,
Canada N2L 3G1;
Email: hsheikh@dspfactory.com
Abstract
:
In this chapter, we describe a hybrid subband adaptive speech enhancement
system, implemented on an efficient ultra-low resource hardware platform
utilizing oversampled generalized DFT filterbanks. Two analysis filterbanks
decompose the two inputs (reference noise and noisy speech) into two sets of
subband signals. In each subband, a subband adaptive filtering noise reduction
block processes the two subband signals to reduce the noise producing a single
signal which is followed by further noise reduction through Wiener filtering.
Next, a synthesis filterbank converts the processed subband signals back into
the time-domain. We have evaluated the performance of the hybrid noise
reduction system in various real-life noise fields occurring in mobile and
vehicular applications. Two closely spaced microphones make recordings in
these noise fields. Signals from one microphone are used directly and represent
the reference noise signal while signals from the other microphone are added
to speech materials chosen from the TIMIT database before being used as the
contaminated primary signal. It is demonstrated that all the noise recordings
closely obey a diffuse noise field model. As the hybrid enhancement system is
specifically designed to handle diffuse noise fields, it outperforms both the
SAF and standard Wiener filtering in all sets of recordings. The superiority of
the hybrid system is especially noted in the case of lowpass noise and intense
noise conditions.
Keywords:
LMS, Wiener filter, subband adaptive filter (SAF), oversampled filterbank,
speech enhancement, diffuse noise, car noise, DFT filterbank, low-resource
system.
