Filtering Performance of Reducing
the Sampling Rate of Sound Card:
Perspectives on Different Signal-to-Noise Ratios
Bing-Yuh Lu*,**, Li-Man Tseng***, Ling-Yuan Hsu**, Shr-Hong Tang**,Yu-Lin Weng**, Man-Na Hsueh***, Mei-Ju Su****, Huey-Dong Wu*****, Jin-Shin Lai*******
Department of Electronic Engineering, Tungnan University, Taiwan, ROC
Department of Information Management, Catholic St. Mary’s Junior College of Medicine, Nursing, and Management,Taiwan, ROC***
Department of Nursing, Catholic St. Mary’s Junior College of Medicine, Nursing, and Management, Taiwan, ROC****
Department of Biomedical Engineering, Yuanpei University, Taiwan, ROC*****
Section of Respiration Therapy, Department of Integrated Diagnostics and Therapeutics, National Taiwan University
Hospital, Taiwan, ROC******
Department of Physical Medicine and Rehabilitation, National Taiwan University Hospital and College of Medicine,National Taiwan University, Taiwan, ROC**

Benjaminee777@hotmail.com, liman@smc.edu.tw, lyhsu@smc.edu.tw, shrhongtang@smc.edu.tw, ylweng@smc.edu.tw, helena@smc.edu.tw,merri1024@gmail.com, hdwuntuh@ntu.edu.tw, jslai@ntu.edu.tw
Abstract— This study presented a theoretical analysis to prove that there exists an optimal sampling frequency to reduce the noise in
the signal to reduce the processes of acoustic digital signal processing. The respiration sounds have been recorded by 2 to 44.1 KHz or
higher sampling rates, however, the optimal frequency might be decided by the noise from environment. This study solves the problem
from the point of theoretical view. The findings were interesting because the noise in a pure sine wave can be reduced by lower samplingrates. The sampling frequency of lung sound recording can be reduced in the range of 2 to 5 KHz. In addition, the results supported toenhance signal-to-noise ratio in the receivers of frequency modulation, under-water acoustics, and other communication applications.
Keyword— noise reduction, sampling frequency, acoustic signal, lung sound, sound card, sonar, SNR.

Bing-Yuh Benjamin Lu received his BS degree in electrical engineering from National Central University
and his MS and PhD degrees in electrical engineering from National Taiwan University in 1988, 1993, and2000, respectively.
He was an instructor at the Department of Electronic Engineering, Tungnan University, New Taipei City,Taiwan, Republic of China in 1992. In 2000, he became an associate professor in the same department. He
joined the Department of Information Management, St. Mary’s Medicine, Nursing, and Management
College, Yi-Lan, Taiwan, Republic of China in 2011, and served as an associate professor and the department
head in the duration of 2011 to 2013. He is currently an associate professor in Department of ElectronicEngineering, Tungnan University, New Taipei City, Taiwan, Republic of China. He is interested in computer
simulation, medical engineering, acoustics, lung sound and educational researches. He is a member of IEEE.
His academic interests in focus on acoustics, medical engineering, computer simulation, educational applications of engineering,and pulmonary signal processing especially about lung sound and pulmonary mechanism.

Liman Tseng is a lecturer in the Nursing Department, St. Mary’s Junior College of Medicine, Nursing andManagement, Yi-Lan, Taiwan. She has a MS degree in nursing, Tzu Chi University in 2005, who attended aPhD degree in public health, in Tzu Chi University in 2009. Her research and teaching interests include nursing
administration, surgical nursing, oncology nursing and pediatrics nursing.

Ling-Yuan Hsu was born in I-Lan, Taiwan, R.O.C., in 1975. He received the M.S. degree in computer scienceand information engineering from National Dong Hwa University, Hualien, Taiwan, in 2004, and Ph.D.
degree in computer science and information engineering at National Taiwan University of Science andTechnology, Taipei, Taiwan, in 2013. Currently, he is an assistant professor in the Department of Information
Management of ST. Mary’s Medicine, Nursing, and Management College. His research interests include
artificial intelligence, image processing, evolutionary computation, and computer networks.

Shr-Hong Tang was born in Taiwan in 1978. He received Ph.D. in Engineering from National Chiao Tung
University (Hsin-Chu, Taiwan) in 2007. His major field of study was applied information technology inengineering. He is currently an assistant profession in St. Mary’s Medicine, Nursing and Management College,and pursuing an advanced degree in computer science from National Taipei University of Education (Taipei,Taiwan)

Yu-Lin Weng received her M.S. degree in Information Management from National Taichung University ofScience and Technology and her MS degrees in Network Learning technology from National CentralUniversity in 2006 and 2008, respectively. Currently, she is pursuing a PhD degree in Information Technologyat National Taiwan University of Science and Technology .She was an instructor at the Department ofInformation Technology, St. Mary's Medicine, Nursing and Management College, Yi-Lan, Taiwan, Republicof China from 2008. She is currently the head of the Registration Section, St. Mary’s Medicine, Nursing, andManagement College. She is interested in digital learning, adaptive testing, and database systems.

Man-Na Hsueh received her MS degree in nursing from National Taipei University of Nursing and Health
Sciences in 2004. Over the past 35 years, she has been teaching at St. Mary’s Nursing School (before 2005)
and St. Mary’s Medicine, Nursing, and Management (after 2005). She was the Director of the Departmentof Students’ Affairs from 1991 to 1997, the Director of the Department of Students’ Internship Affairs from2004 to 2005, and the Representative President and Director of the Department of Academic Affairs in 2005.
She is currently the head of Department of Nursing at St. Mary’s Junior College of Medicine, Nursing, andManagement . She is interested in elder person’s health care and in community medicine.

Mei-Ju Su received Ph.D. degree at Graduate Institute of Electronics Engineering, National Taiwan
University since 2004 to 2010, Master degree at Department of Electrical Engineering, Syracuse Universitysince 1996 tp 1997. Now, her researches focus on biosignal processing, medical device, tele-healthcare
system, and sensor design. She had been worked at Industry for 8 years since 1998~2005 on network IC
design and SiS Company, medical instrument system design at Biomedical Technology and Device ResearchLaboratories of Industrial Technology Research Institute. Now she is the associate professor of departmentof Biomedical engineering, Yuanpei University.

Huey-Dong Wu was graduated with a M.D. degree from Medicine Department of National Taiwan
University in 1984. He received resident training in National Taiwan University Hospital (NTUH) and trained
as visiting scholar in ULCA later. He service in the Department of Internal Medicine and Department ofIntegrated Diagnostic & Therapeutics in National Taiwan University Hospital (NTUH) till now. He is thechief of the division of Respiratory Care, Department of Integrated Diagnostic & Therapeutics in NTUH. His
academic interests in focus on respiratory care, pulmonary pathophysiology and pulmonary signal processing
especially about lung sound and pulmonary mechanism.

Jin-Shin Lai was born in Taipei, Taiwan, Republic of China (R.O.C.) in 1949. He received the M.D. degreefrom the Medical School of National Taiwan University, Taipei, Taiwan in 1974. He completed residency
training in the Department of Physical Medicine and Rehabilitation, National Taiwan University Hospital,Taiwan in 1978.He was a Lecturer, Associate Professor, and Professor of Medical School, College of Medicine,National Taiwan University in 1980, 1984 and 1996, respectively.
Now, he is the Director of Health Science and Wellness Center, National Taiwan University and Director ofSports Medicine Center, National Taiwan University Hospital. His professional interests include medical
informatics, sports medicine, rehabilitation medicine, biomechanics, and rehabilitation engineering. He andhis research group had published a series of studies about Physiological Effects of Tai Chi Chuan Training.
Prof. Lai has been the Chairman of School of Rehabilitation Medicine (1988-1992), Chairman of School of Occupational Therapy(1992-1998), Chairman of Department of Physical Medicine & Rehabilitation (1993-1999), Chief of Division of Medical
Informatics (2001-2007), College of Medicine, National Taiwan University, respectively. He also served as the Chairman ofDepartment of Information Technology & Service, National Taiwan University Hospital (1998-2004), and elected as the Presidentof Rehabilitation Medicine Association of Taiwan (R.O.C.) 1993-1999, the President of Sports Medicine Association of Taiwan(R.O.C.) 1997-2001, the Chairman of Scientific Commission of Asian Federation of Sports Medicine (AFSM) 1990-2000, theTreasurer of Asian Federation of Sports Medicine (AFSM) 2001-2004 and the Chair of HL-7 Taiwan (2005-2009).