2.4 Echo and reverberation  (Page 2/3)

Copying a block from the echo subsystem

Double click on the “ Effect 1” subsystem. Cut-and-paste a copy of the echo block as follows: while left-clicking the mouse, mark the area to be copied.

Release the left button on the mouse.

From pull-down menu, select Edit ->Copy (or Ctrl + C)

Blocks dropped onto effect 2 subsystem

Return to the “Effect 2” subsystem and Edit ->Paste (Ctrl + V) into the model.

Flipping the blocks

The blocks are facing the wrong way. Turn them round using Format ->Flip Block.

Changing the integer delay for reverberation.

Because the sound goes round several times with reverberation, a shorter delay time can be used. Here the delay time is 0.1 seconds.

Set the “Number of delays” to 800 then click on “OK”.

Completing the reverberation subsystem

Connect the blocks as shown below. Change the title to “Reverberation Subsystem”.

Returning to the parent system

From the Toolbar, select the “Up Arrow” icon. This returns you to the next higher level.

The improved echo subsystem

The final subsystem to be implemented will be “Improved Echo”. This is based on the “Echo” subsystem, but with several delay paths.

The complete improved echo subsystem

Double click on the “Effect 3” subsystem box. The required components are shown below.

Implementing the improved echo subsystem

You should now have enough knowledge to implement this subsystem block without further assistance. This time you are on your own!

Building the model

Select Tools ->Real-Time Workshop ->Build Model.

Running the model

Microphone straight through to loudspeakers

To check out the microphone and loudspeakers, set the DIP switches on the C6713 DSK as follows:

The microphone is fed directly to the loudspeakers without any digital signal processing.

Switch position for echo

To run the “Echo” subsystem, set the DIP switch to 1.

Switch position for reverberation

To run the “Reverberation” subsystem, set the DIP switch to 2.

Switch position for improved echo

To run the “Improved Echo” subsystem, set the DIP switch to 3.

Some things to try

Change the echo delay

Change the value of the “Integer Delay” block for echo. Listen to the effect of using short and long delays. Set the delay time to a large value and sing a round such as “Frere Jacques” or “Row, Row, Row your Boat”.

Change the amount of reverberation gain

In the “Reverberation Subsystem” block, change the “Gain” from 0.8 to higher and lower values. Notice how the system can become unstable if the gain is too large.

Modify the improved echo subsystem

In the “Improved Echo Subsystem”, you may wish to experiment with the number of delay elements, the delay times and the amounts of gain. Try to make the echo as realistic as possible.

Create your own subsystem

Add your own subsystem block and add your own signal processing. You might want to design a subsystem with both echo and reverberation.

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