IVR PLAYBACK BASED ON DID
SOUND FILES
Place the sound files under the default folder /var/lib/asterisk/sounds/en/
In this example we created a folder DID and add some files into it:
The file names must be DID.wav
In the example we'll use some internals DID (500,700,800,900) 
IVR DESIGN
You don't need specify the file extension. If you place the audio file in a different folder, you need to insert the entire file path.