1. International Journal of Electronics and Communication Engineering & Technology (IJECET), ISSN 0976
– 6464(Print), ISSN 0976 – 6472(Online), Volume 5, Issue 4, April (2014), pp. 50-56 © IAEME
50
SEGREGATION OF ACOUSTIC SIGNAL USING WAVELET TRANSFORM
Er. Tarana Afrin Chandel
Department of Electronics and Communication Engineering, Integral University,
Lucknow, India
ABSTRACT
Auscultation, the technique of listening to heart sound with a stethoscope, thus diagnosing
heart valve disorder. In Phonography (PCG) the heart sound are recorded using stethoscopes and
displayed on the PC/laptop rather than listening to the heart sound as done in traditional
auscultation. More detail is accessible visually, because the analysis is not limited by the human
audibility or experience of the physician while listening. The heart disease can be detected by
the symptoms of pathology appears and this makes it a high potential diagnosis test for future
the aim of this study is to detect various disease using PCG signals Many diagnostic feature
can be extracted using PCG which otherwise require test like Electrocardiography (ECG) or
Echocardiography. In this paper we present a method that is channel noise reduction of heart sound.
The fetal sound signals are detected and reconstructed by utilizing wavelet transform based on
signal.
Keywords: Signal to noise ratio (SNR), Peak signal to noise ratio (PSNR), PCG signal,
Wavelet transform.
I. INTRODUCTION
Auscultation of the heart remains an important examination for the detection of
cardiovascular disease. The auscultatory exam is expedient and cost effective. When completed by an
experienced clinician, auscultation carries a high predictive value for identification of many serious
heart diseases. Definitive diagnosis may be possible by auscultation, as when classic murmurs of
patent ductus arteriosus or mitral regurgitation are identified. Often the combination of signalment,
cardiac and pulmonary auscultation, and general physical examination point to a tentative cardiac
diagnosis. This presumption can then be confirmed, refined, or refuted by echocardiography (for
valvular disease, pericardial disease, cardiomyopathy) or by electrocardiography (for arrhythmias).
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2. International Journal of Electronics and Communication Engineering & Technology (IJECET), ISSN 0976
– 6464(Print), ISSN 0976 – 6472(Online), Volume 5, Issue 4, April (2014), pp. 50-56 © IAEME
51
The essential abnormalities of cardiac auscultation include: abnormal heart rate (bradycardia,
tachycardia), irregular cardiac rhythm, abnormal intensity of heart sounds, extra heart sounds, cardiac
murmurs, and pericardial friction rubs.
II. TECHNIQUES FOR CARDIAC AUSCULTATION
The choice of a stethoscope is very personal. The traditional stethoscope has an operator
selected diaphragm and bell. Some stethoscope designs allow a single chest piece to function as both
a bell and a diaphragm. However, some of the newer models combine both “adult” and “pediatric”
single chest piece stethoscopes into one rotating head. Amplified stethoscopes generally are not
recommended because of the potential for blooming artifacts and distortion; however, they can be
useful for those with a hearing impairment.
The clinician must understand that many heart sounds fall below the frequency-threshold
limit; accordingly, careful auscultation is necessary to detect the vibrations that are audible. The
stethoscope tube length should not be excessively long, the binaural and ear pieces should be directed
so that their orientation is rostral and aligned with the ear canals, and earpieces should be inserted
snugly but comfortably to obtain an airtight seal. The flat diaphragm chest piece is applied gently but
firmly to the chest to accentuate higher frequency sounds such as normal heart and breath sounds and
most cardiac murmurs. The bell, which is applied lightly to achieve an airtight seal, enhances
detection of lower frequency sounds such as the third and fourth heart sounds. The bell is also useful
for detection of the more uncommon diastolic murmurs. The entire pericardium is examined, with
particular attention directed to the cardiac valve areas. [1, 2]
While the exact anatomic location of the valve areas depends on the chest conformation, and
size of the heart, a common relative location is found from cranial to caudal: pulmonic–aortic–
tricuspid–mitral with the tricuspid valve on the right. A useful clinical pointer is to first palpate the
left apex beat where mitral sounds radiate and the first heart sound is best heard. Find other valve
areas from this point. The aortic valve area is located craniodorsal to the left apex and the second
heart sound is best heard there. Once the aortic second sound is identified, the stethoscope can be
moved one interspace’s cranial and slightly ventrad (over the pulmonary valve area).The pulmonary
artery extends dorsally from the pulmonic valve. The tricuspid valve is over the right hemi thorax,
cranial to the mitral area, and covers a relatively wide area. The LV outlet is in the center of the heart
and aortic murmurs usually radiate well to each hemi thorax. Cardiac apex and cardiac base are
commonly used expressions to designate the regions ventral and dorsal to the atrioventricular groove.
The mitral and tricuspid valvular sounds often radiate ventrally towards the apex. Murmurs
originating at the semi-lunar valves and great arteries are detected best over the base. The author
typically defines auscultation areas as caudal (chest piece centered over the apex beat), cranial (1–2
intercostals spaces cranial to the apex), left sternal and right sternal. Fig1 shows typical auscultation
sites to place microphone.
Fig.1: Typical auscultation sites to place microphones

3. International Journal of Electronics and Communication Engineering & Technology (IJECET), ISSN 0976
– 6464(Print), ISSN 0976 – 6472(Online), Volume 5, Issue 4, April (2014), pp. 50-56 © IAEME
52
III. MECHANISM FOR TRANSIENT CARDIOVASCULAR SOUND
In this section we show the mechanism for the production of transient cardiovascular sound.
Cross sectional view of human heart is shown in fig2. The human heart has four chambers, two
superior atria and two inferior ventricles. The atria are the receiving chambers and ventricles are the
discharging chambers.[3] Normal heart sounds are associated with valves closing, causing changes in
blood flow.[4]
The main frequency range of the PCG signal is in the range of 10 - 35 KHz however in the
case of artificial heart valves frequencies up to 50 KHz is recorded. Heart sound is generated by the
vibration of heart valves during their opening and closure and by the vibration of myocardium and
the associated structure. The sound generated by the human heart during the cardiac cycle consists of
two domain component called the first heart sound S1 and the second heart sound S2. Fig2. Show a
phonocardiogram signal from a healthy person containing the first heart sound (S1) and the second
heart sound (S2).
Fig. 2: Cross-section of a typical human heart
The first heart sound S1, forms the lub-of lub-dub and is composed of component M1 and T1.
Normally M1 precedes T1 slightly. It is caused by sudden blocks of reversal blood flow due to closure
of the atrioventricular valves (tricuspid) and mitral (bicuspid) at the beginning of ventricular
contraction, or systole. When the ventricles begin to contract, so do the papillary muscles in each
ventricle. The papillary muscles are attached to the tricuspid and mitral valves via chordate
Fig. 3: A phonocardiogram signal from a healthy person containing the first heart sound (S1) and
the second heart sound (S2)
tendineae, which brings the cusps or leaflet of the valve close, the chordae tendineae also prevent the
valve from blowing into the atria as ventricular pressure rise due to contraction. The closing of the
inlet valves prevents regurgitation of blood from the ventricles back to atria. The S1 sound results
from reverberation within the blood associated with the sudden block of flow reversal by the
valves.[3] If M1 occurs slightly after T1, then the patient likely has a dysfunction of conduction of
the left side of the heart such as a left bundle branch block.

4. International Journal of Electronics and Communication Engineering & Technology (IJECET), ISSN 0976
– 6464(Print), ISSN 0976 – 6472(Online), Volume 5, Issue 4, April (2014), pp. 50-56 © IAEME
53
The second heart sound S2, forms the "dub" of "lub-dub" and is composed of components
A2 and P2. Normally A2 precedes P2especially during inspiration when a split of S2 can be heard. It is
caused by the sudden block of reversing blood flow due to closure of the semilunar valves (aortic
valve and pulmonary valve) at the end of ventricular systole and the beginning of ventricular diastole.
As the left ventricle empties, its pressure falls below the pressure in the aorta. Aortic blood flow
quickly reverses back toward the left ventricle, catching the pocket-like cusps of the aortic valve, and
is stopped by aortic valve closure. Similarly, as the pressure in the right ventricle falls below the
pressure in the pulmonary artery, the pulmonary valve closes. The S2 sound results from
reverberation within the blood associated with the sudden block of flow reversal. Splitting of S2, also
known as physiological split, normally occurs during inspiration because the decrease in intrathoracic
pressure increases the time needed for pulmonary pressure to exceed that of the right ventricular
pressure. A widely split S2 can be associated with several different cardiovascular conditions,
including right bundle branch block, pulmonary stenosis, and atrial septal defects. [5, 6, 7]
Heart murmurs are produced as a result of turbulent flow of blood strong enough to produce audible
noise. [8, 9] They are usually heard as a whooshing sound. The term murmur only refers to a sound
believed to originate within blood flow through or near the heart; rapid blood velocity is necessary to
produce a murmur. It should be noted that most heart problems do not produce any murmur and most
valve problems also do not produce an audible murmur. Heart murmurs of aortic (stenosis,
regurgitation) and mitral (stenosis, regurgitation) is in fig 4.
Fig. 4: Heart murmurs
IV. METHOD
Due to the overlap of the heart sound components and the noises caused by other internal
organs, a full analysis of the heart sound in the time-domain is difficult. The heart sound is more
important than the heart rate and accordingly we will subsequently restrict the processing of heart
sound to the frequency domain. Wavelet transform is used for the segregation of PCG signal, as
wavelet helps to do multi-resolution analysis to achieve time and frequency domain.
Wavelet functions used for signal analysis are derived from the initial function W(t) forming basis
for the set of functions.
Wm, k (t) = (1/√a) W (1/a (t – b)
= (1/ √2m
) W (2-m
t – k) (1)
For discrete parameters of dilation a =2m
and translation

5. International Journal of Electronics and Communication Engineering & Technology (IJECET), ISSN 0976
– 6464(Print), ISSN 0976 – 6472(Online), Volume 5, Issue 4, April (2014), pp. 50-56 © IAEME
54
b =k 2m
.Wavelet dilation, which is closely related to spectrum compression, local and global signal
analysis. For short-time Fourier transform, as in the case of speech signals, a short-time stationary
property for heart sounds is assumed, which conveniently allows a STDFT analysis. [12]
N −1
X [n, k] = ∑ x ∗ w [m + (n − 1) S] exp (-j 2π km) (2)
m=0 N
Where n is the frame index, k is the frequency index, N is the frame length, S is the frame
shift and w denotes the window. Unlike speech signals, where the vocal track is changing after each
20-25ms, heart sounds are more stationary and therefore the window length should be larger. The
optimal window length was found to be about 500ms through experiments conducted in subsequent
section. A related issue is the effect of the window shift on the performance of the pattern recognition
method. Gaussian white noise mixture modelling is used between samples in order to accurately
estimate the probability distribution. [7]
Since the human heart sound is quasi-stationary with much longer segment than speech and
consequently the standard 20-25ms frame length for speech processing did not matched accurately.
This point was detected by the experiments done. The frame length is very important issue. The
standard in speech frame length is ineffective for the heart sounds, yielding less than 70% accuracy.
Thus 512ms is shown to be the optimal choice of frame length.
After scaling the component at different threshold levels, wavelet coefficient reaches zero if it
is below threshold level and contains the same value if it is above the threshold level at last the
filtered and reconstructed signals can be retrieved by wavelet inverse transform.
V. RESULT
Comparative analysis is done between two signal ie original PCG signal mixed with low
intensity Gaussian noise and the other signal is original PCG signal mixed with high intensity
Gaussian noise. Simulated results are obtained through signal to noise ratio and peak signal to noise
ratio of the denoise signal using wavelet transform.
SNR= power of signal/ power of noise (1)
PSNR= 10*log10 ((N*(X^2))/E diff (2)
Table. 1: Signal to noise ratio for sampled signals
Level /
wavelet
Norma
heart
sound
Artial
Spectral
defect
Artial
Spectral
defect
Patent
Ductus
Arterios
us
db2 7.5656 3.876 4.269 1.0234
db4 2.8190 6.358 6.853 5.293
db6 2.1053 6.213 6.248 4.967

6. International Journal of Electronics and Communication Engineering & Technology (IJECET), ISSN 0976
– 6464(Print), ISSN 0976 – 6472(Online), Volume 5, Issue 4, April (2014), pp. 50-56 © IAEME
55
IV. CONCLUSION
Phonocardiography is a method of accessory value in cardiac conditions. It is technically a
difficult procedure. It has been of greatest help in the timing of heart sounds having abnormal
components or unusual accentuation of normal components-split sounds, third sounds, auricular
sounds, and gallop rhythms. This difficulty is overcome using wavelet transform. In this paper
different cardiac disease was detected using wavelet transform. In only rare instances are the data
provided by phonocardiography of critical importance in diagnosis. Such instances include the
recording of murmurs which are inaudible due to masking and fatigue effects on the ear from
previous loud sounds; the demonstration of true presystolic murmurs of mitral stenosis; and the
definition of characteristic patterns of pulmonic and aortic stenosis. The discriminating use of
phonocardiography will undoubtedly be increasingly helpful in the diagnosis of valvular and
congenital heart disease.
ACKNOWLEDGMENT
The authors would like to thank Dr. Shefta T Chandel for her contribution to prepare this
paper. Also the author would like to thank Prof. (Dr.) S. Hasan Saeed, HOD, ECE Department I.U
for his whole hearted support. Furthermore, the authors would like to acknowledge their friends and
colleague for their fruitful and constructive comments.
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