title: Enhancement of lung sounds based on empirical mode decomposition and Fourier transform algorithm.
abstract: OBJECTIVE
  There is always heart sound (HS) signal interfering during the recording of lung sound (LS) signals. This obscures the features of LS signals and creates confusion on pathological states, if any, of the lungs. In this work, a new method is proposed for reduction of heart sound interference which is based on empirical mode decomposition (EMD) technique and prediction algorithm.
  
  
  METHODS
  In this approach, first the mixed signal is split into several components in terms of intrinsic mode functions (IMFs). Thereafter, HS-included segments are localized and removed from them. The missing values of the gap thus produced, is predicted by a new Fast Fourier Transform (FFT) based prediction algorithm and the time domain LS signal is reconstructed by taking an inverse FFT of the estimated missing values.
  
  
  RESULTS
  The experiments have been conducted on simulated and recorded HS corrupted LS signals at three different flow rates and various SNR levels. The performance of the proposed method is evaluated by qualitative and quantitative analysis of the results.
  
  
  CONCLUSIONS
  It is found that the proposed method is superior to the baseline method in terms of quantitative and qualitative measurement. The developed method gives better results compared to baseline method for different SNR levels. Our method gives cross correlation index (CCI) of 0.9488, signal to deviation ratio (SDR) of 9.8262, and normalized maximum amplitude error (NMAE) of 26.94 for 0 dB SNR value.
authors.affiliation: Department of Electronics and Communication Engineering, National Institute of Technology, Bhopal, India. Electronic address: ashokrpe@gmail.com.
authors.forename: Ashok
authors.initials: A
authors.lastname: Mondal
authors.affiliation: Department of Electronics and Communication Engineering, National Institute of Technology, Bhopal, India.
authors.forename: Poulami
authors.initials: P
authors.lastname: Banerjee
authors.affiliation: Department of Electronics and Communication Engineering, National Institute of Technology, Bhopal, India.
authors.forename: Ajay
authors.initials: A
authors.lastname: Somkuwar
mesh_terms: D000465:Algorithms; D005583:Fourier Analysis; D006801:Humans; D008168:Lung / Q000503:physiopathology*; D008962:Models, Theoretical; D012135:Respiratory Sounds
keywords: Empirical mode decomposition; Fast Fourier transform; Heart sound; Lung sound; Power spectral density; Spectrogram