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Wavelets can be used in a wide range of applications, one of which is noise reduction. This module shows a real-time implementation of a wavelet-based noise reduction in the DSK6713. A Simulink model is created for simulation, and afterwards used for DSP code generation.

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.

Simulation

The Simulink model described here is based on a MATLAB Demo.

Opening the model

Open WaveletDenoising.mdl

Opening WaveletDenoising.mdl

Running the model

Run the model. The colors change to show the different filter channels. Green = high frequency.

Wavelet Model Showing Color Coding

Scope output

The scope output shows how the random noise has been separated out (Residual).

Scope Output

Monitoring the dyadic filter outputs

Add an extra scope as shown in Figure 4 to display the Diadic Filter Outputs.

Monitoring the Dyadic 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.

Noise Levels at Dyadic Filter Outputs

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.

Noise Levels at Dyadic Filter Outputs

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.

Threshold only applied to Out1

Changing the delay alignment

Double-click on the “Delay Alignment” block. Temporarily remove the delays on Out1 and Out2.

Removing the Delay Alignments

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.

Real-time model for ti c6713 dsk

Texas instruments c6713 dsk setup

Texas Instruments C6713 DSK Setup

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Source:  OpenStax, From matlab and simulink to real-time with ti dsp's. OpenStax CNX. Jun 08, 2009 Download for free at http://cnx.org/content/col10713/1.1
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