Introduction
Wavelets can be used in a range of applications, one of which is noise reduction.
This laboratory shows how to design a model of Wavelet Noise Reduction using Simulink and run it on a Texas Instruments C6000 DSP.
Objectives
- Design a model of Wavelet Noise Reduction for the Texas Instruments C6000 family of DSP devices using MATLAB® and Simulink®.
- Modify an existing Simulink demonstration model.
- Run the project on the Texas Instruments C6713 DSK with a microphone and computer loudspeakers / headphones.
Level
Intermediate. Assumes prior knowledge of MATLAB and Simulink. It also requires a theoretical understanding of wavelets and some knowledge of Texas Instruments DSPs.
Hardware and software requirements
This laboratory was originally developed using the following hardware and software:
- MATLAB R2006b with Embedded Target for TI C6000.
- Code Composer Studio (CCS) v3.1
- Texas Instruments C6713 DSK hardware.
- Microphone and computer loudspeakers / headphones.
Related files
- Powerpoint Presentation WaveletDenoising.ppt
- Simulink Model for Simulation- WaveletDenoising.mdl
- Simulink Model for Real-Time WaveletDenoisingDSKC6713.mdl
Simulation
Simulink model
The Simulink model described here is based on a MATLAB Demo.
Opening the model
Open WaveletDenoising.mdl
Running the model
Run the model. The colors change to show the different filter channels. Green = high frequency.
Scope output
The scope output shows how the random noise has been separated out (Residual).
Monitoring the dyadic filter outputs
Add an extra scope as shown in Figure 4 to display the Diadic Filter Outputs.
Analysis of diadic filter outputs
It can be seen that the noise is on Out1, Out2 and Out3. The clean input signal is on Out4.
Modifying the dead zone
Double-click on the “Soft Threshold” block. This is the actual noise reduction stage. The fields are in order Out1, Out2, Out3 and Out4.
Here Out1 has been given a threshold of 3. This means that only values>3 are let through.
Out2, Out3 and Out4 have been given the value of 0. This means the whole signal is let through.
The output is shown in Figure 6. Note that the noise associated with Out2 and Out3 have not been reduced.
Changing the delay alignment
Double-click on the “Delay Alignment” block. Temporarily remove the delays on Out1 and Out2.
Run the model to see the effect.
Summary of simulation
From practical experimentation using the Simulink model, you should now understand how wavelet denoising works.