← Back

Wavelet Analysis

Haar DWT, reconstruction, Daubechies, and Fourier comparisons.

Wavelet Analysis & Multiresolution Handbook

Mathematical Principles & Theorems

Investigates time-frequency localized signal analysis. Continuous Wavelet Transform (CWT): \(W(a, b) = \frac{1}{\sqrt{|a|}}\int_{-\infty}^\infty x(t) \psi^*\left(\frac{t-b}{a}\right)dt\) with scale \(a > 0\) and translation \(b\), overcoming Heisenberg-Gabor uncertainty limitations of the Short-Time Fourier Transform. Discrete Wavelet Transform (DWT) via Haar wavelet \(\psi(t) = \mathbf{1}_{[0, 1/2)}(t) - \mathbf{1}_{[1/2, 1)}(t)\) and Daubechies filter banks. Wavelet shrinkage denoising via soft/hard thresholding of detail coefficients.

Operating Instructions

  • Select test signal profile (Doppler, Blocks, Bumps, Noisy Sinusoid).
  • Set threshold \(\tau\) using the numeric value box and toggle Soft / Hard thresholding.
  • Click Run Decomposition to compute Multiresolution Analysis (MRA) detail and approximation levels.
  • Inspect the 2D CWT scalogram time-frequency heatmap and reconstructed denoised signal.

Controls

Daubechies D4 Wavelet. 2 vanishing moments, compact support [0,3].

Original Signal (N=64)
Wavelet Coefficients (by level)
Levels
Max coeff |W|
Energy retained
Sparse coeffs
Original vs Reconstructed
MSE (error)
Coeffs zeroed
Compression ratio
D4 Scaling coefficients h:
h₀ = (1+√3)/4√2
h₁ = (3+√3)/4√2
h₂ = (3−√3)/4√2
h₃ = (1−√3)/4√2
Wavelet families:
Haar (D2): simplest, discontinuous
Daubechies D4: 2 vanishing moments
Daubechies D6: 3 vanishing moments
Symlets: improved symmetry
Fourier Transform
  • Global frequency content
  • Perfect freq resolution
  • No time localization
  • Bad for transient/non-stationary signals
  • Gibbs phenomenon at discontinuities
Wavelet Transform
  • Time-frequency localization
  • Multi-resolution analysis
  • Good for transients & edges
  • Used in JPEG2000, EEG, audio
  • Must choose right wavelet family