MATLAB Examples

Wavelet Reconstruction and Noise Reduction

This example uses the Dyadic Analysis Filter Bank and Dyadic Synthesis Filter Bank blocks to show both the perfect reconstruction property of wavelets and an application for noise reduction.


Exploring the Example

Open the Operation block dialog and select either Remove noise or Perfect reconstruction. The selection will enable the corresponding enabled subsystem.

Opening the Wavelet Reconstruction subsystem shows an Analysis Filter Bank followed by the Wavelet Reconstruction subsystem. The net effect of these two operations is perfect reconstruction of the input signal.

Opening the Noise Reduction subsystem shows the same wavelet blocks but with a soft threshold applied to the transformed signal bands. By attenuating the higher frequency bands, the high frequency noise is reduced. You can adjust the threshold levels to see the effects of attenuation on the denoising characteristics of the system.

Run the example to view the input and output signals and the difference between them. Note that for perfect reconstruction, the difference appears to be zero. However, due to numerical effects, there is a small difference that can be seen in the display of the running RMS display.

Available Example Versions

Floating-point sample-based version: dspwavelet

Floating-point frame-based version: dspwavelet_frame

Fixed-point sample-based version: dspwavelet_fixpt