Please make sure that you follow the below steps when convert your SWF file to AVI video with SWF & FLV Toolbox:
1) Browse to the specific file and add it to the Task List;
2) Select the action for the added file (go to "Video" tab);
3) Click on "Add action" button;
4) Tick all the files you have added the actions for in the Task List (this action is needed only if "Mark new tasks automatically" option is disabled);
5) Click "Process all Tasks" button.
If you are converting SWF to AVI make sure that you select the proper sound device in the settings.
If you select "Frame-by-frame" option check "Add original streaming sound" by default.
If you select "SWF interact video" check "Add captured sound" and then click "Sound device" button to select the one which will let you record the sound you need.
Also, please, check the following article at Eltima Wiki:http://wiki.eltima.com/user-guides/swf-flv-toolbox/video.html