Copyrights @Kalahari Journals Vol. 7 No. 1 (January, 2022) International Journal of Mechanical Engineering 2810 ISSN: 0974-5823 Vol. 7 No. 1 January, 2022 International Journal of Mechanical Engineering Performance Analysis Of Dwt Based Denoising Of Vibration Signals: A Case Study Of Heart Sound Signals Ravindra Manohar Potdar Bhilai Institute of Technology, Durg, India potdar.bit@gmail.com Arun Kumar Bhilai Institute of Technology, Durg, India arun.kumar@bitdurg.ac.in Ramesh Kumar Govt. Polytechnic, Simdega, Jharkhand, India rk_bitd@rediffmail.com Abstract – Discrete Wavelet Transform (DWT) is a very powerful and effective technique to remove in-band noises corrupting any sounds arising out of vibrations. Phonocardiogram, being the record of the sounds generated by heart due to its electro- mechanical activities carry information regarding the status of cardiovascular system. Hence, the noises corrupting the PCG are required to be removed. The efficacy of denoising process largely depends upon the choices of proper Mother Wavelet (MWT) function, the number of decomposition level (DL)and the Thresholding Function (TF) applied after decomposition. The present work aims at optimal selection of the type of MWT, DL and TF to obtain lowest values of Mean Square Error (MSE) and Root Mean Square Error (RMSE). Five different types of orthogonal MWT, DL up to 10 and seven TFs are applied for analysis of performance of the denoiser. The performances of every combination are compared through exhaustive experiments performed in the MATLAB environment. After analyzing the results obtained, it was observed that sym20 as the MWT with a DL of 10 with a soft TF namely Bayes Soft in removing noises from PCG. Keywords – Denoising, DWT, MSE, PCG, RMSE, Vibration Signal I. INTRODUCTION Phonocardiogram signal is of interest for condition based monitoring of cardiovascular functions and the physiological status of the heart. Heart is considered as an electro-mechanically initiated pump with two stages and four chambers. The main job of the heart is to circulate blood throughout the body to supply energy for their functioning using oxygenated blood and at the same time to collect the impure blood from the organs. The vessels associated with the heart are responsible for carrying the blood. The flow of blood is controlled through the valves instilled in the heart. The pressure built inside the heart due to its rhythmic contraction and expansion controls the opening and closing of the heart valves. Such phases of the heart are commonly known as systolic and diastolic phase. Sound is created during any mechanical activity so as the heart also creates sound. The frequency may or may not be in the audible range. The sound created due to functioning of the heart normally falls in the audio range of frequency and hence is audible by using an acoustic arrangement called the stethoscope. To monitor the activities occurring in the cardiovascular system, physicians often take the help of stethoscope to hear the sounds generated by the heart. This is the cheapest method of monitoring and diagnosis in a non-invasive manner for any disorder occurring in the cardiovascular system. However, this technique being very much subjective solely depends upon the skill, experience and expertise of the concerned physicians for accurate diagnosis. Hence, to avoid any medico-legal litigation, the physicians normally refer the patient for costly diagnostic tests involving automated techniques. The major hindrance in feeling the heart sound captured by stethoscope is that it does not support visual display. Phonocardiogram (PCG), which is an electronic record of the heart sound signal (HSS), helps to obtain audio-