Usually the immediate consequence of an EH is that a script is called. The script does whatever you need to do. You can add the EH to a whole bunch of units and the script called by it checks the circumstances of that particular firing and creates consequences - like sound files - accordingly. Be careful though, if you add an EH fired to every unit on the map and it launches a long script, you're going to get lag. EHs themselves cause very little lag, but if you are cavalier with them the consequences can be a severe problem.
What is the underlying situation here? What are you trying to achieve?