2.4 Echo and reverberation

Introduction

Echo and Reverberation are two of the simplest applications of Digital Signal Processing (DSP). This laboratory shows how models of Echo and Reverberation can be designed using MATLAB and Simulink, and run them in real-time on the Texas Instruments C6000 DSPs.

Objectives

• Design models of Echo and Reverberation for the Texas Instruments C6000 family of DSP devices using MATLAB® and Simulink®.
• Modify an existing Simulink model.
• Run the model in real-time on the Texas Instruments C6713 DSK.

Level

Beginner - Assumes only very basic knowledge of MATLAB and Simulink. It is suitable for students with limited 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 - EchoAndReverberation.ppt
• Simulink Model for Echo Simulation - EchoUsingWav.mdl
• Simulink Model for Reverberation Simulation - ReverberationUsingWav.mdl
• Simulink Model for Real-Time - EchoAndReverberationDSKC6713.mdl
• Audio Template for the DSK6713 C6713_Audio_Template.mdl

Simulation

We shall start by running the Echo and Reverberation Simulink models. These use .wav files as the inputs.

Echo using wave file

Opening the echo simulink model

From MATLAB, open EchoUsingWav.mdl

Changing the delay time

Double-click on the “Delay” block and change the “Delay (samples)” to a different value.

Run the model and hear how the effect has changed. Try a few different settings between 100 and 20000 “Delay (samples)”.

Reverberation using wave file

Opening the reverberation simulink model

From MATLAB, open ReverberationUsingWav.mdl

Changing the delay time

Double-click on the “Delay” block. Change the “Delay (samples)” to a different value then run the model and listen to the effect.

Changing the gain

Double-click on the “Gain” block. Change the “Gain” to 0.95 then run the model. Listen to the effect.

Questions

• Why does Reverberation require a shorter delay time than echo?
• What effect does the “Gain” block have on the stability of the reverberation system?

Real-time model for ti c6713 dsk

Texas instruments c6713 dsk setup

Alternatively, you can use computer loudspeakers.

Connect the C6713 hardware to a USB port of the computer and turn on the supply to the board.

If the board is powered, then the green LED lights on the board will come on during self-test.

Starting code composer studio

The stages required to implement Echo and Reverberation are now described.

Starting code composer studio

Start Code Composer Studio for C6713 DSK and use Debug ->Connect