Signal processing design to improve speech signal
quality through spectrum
Muhammad Tahir Zia
Bachelors Computer Engineering
Lahore, Pakistan
u2021465@giki.edu.pk
Abstract—This project focuses on the design and implementa-
tion of a signal processing system to enhance speech signal quality
through spectral processing. The primary challenge addressed
is the presence of undesired noise in speech signals, degrad-
ing their overall quality. The system employs a combination
of high-pass filtering, Short-Time Fourier Transform (STFT),
spectral subtraction, and post-processing techniques to achieve
noise reduction and enhance the clarity of the speech signal.
The field of signal processing stands as a cornerstone for
transformative developments, especially in the realm of speech
and audio processing. In this project, primary focus is on the
meticulous design and implementation of a signal processing
system dedicated to elevating the quality of speech signals.
The overarching challenge that motivates this endeavor is the
omnipresent interference of undesired noise within speech signals,
a ubiquitous issue that detrimentally impacts their overall clarity
and intelligibility. Speech signals, being particularly susceptible to
noise from diverse sources, necessitate sophisticated techniques to
extract and enhance their intrinsic qualities. The proposed system
embraces a synergistic blend of signal processing methodologies,
with a key emphasis on spectral processing techniques. Through
a strategic combination of high-pass filtering, Short-Time Fourier
Transform (STFT), spectral subtraction, and post-processing
methodologies, main objective is to fashion a system that not
only mitigates noise but enhances the clarity and fidelity of the
speech signal.
CE341 - Signals and Systems
I. INTRODUCTION
Speech signal processing is vital for various applications,
with noise reduction being a critical aspect. This project
focuses on creating a signal processing system to enhance
speech signal quality by removing noise components. The
system utilizes a combination of high-pass filtering, spectral
analysis, noise reduction, and post-processing techniques.
II. DESIGN PHASE
Used MATLAB, a renowned software specializing in signals
and systems analysis, to develop the design. Utilizing various
signal processing techniques and system configurations, lever-
aged MATLAB’s robust simulation tools to achieve desired
output. Throughout the design process, primary focus was
on addressing real-world scenarios by adhering to standard
signal processing principles and tackling common challenges
encountered in practical applications. Emphasizing simplicity
and practicality, Goal was to ensure that the design could be
978-1-6654-5992-1/22/$31.00 ©2022 IEEE
readily applied in real-world signal processing setups, aiming
for its effective utilization in practical applications.
A. High Pass Filter
A high-pass Butterworth filter of order 4 with a cutoff
frequency of 200 Hz is chosen for pre-processing. This filter is
effective in attenuating low-frequency noise while preserving
speech components.
B. Spectral Analysis
Spectral analysis is performed using the Short-Time Fourier
Transform (STFT). A window size of 256 with 50 percent
overlap is selected to balance time and frequency resolution.
C. Noise Reduction
Spectral subtraction with noise estimation is employed to
reduce noise. Noise spectrum is estimated through simple
averaging, and subtraction is performed with thresholding.
D. Post Processing
Optionally, post-processing includes inverse STFT to trans-
form the enhanced spectrum back to the time domain.
