Add A Rollover Sound To A Standard Button In Flash?

Can someone tell me the simplest way to add a rollover sound to a standard button in flash ? I was trying to get a small chirp sound to play on rollover of a button. Im using the standard flash button creation hierarchy. Once the fourstages of the button are set. I created a layer above it called sounds then added a blankkeyframe to the over position and dragged the chirp mp3 file onto the stage over the button. Then when i run the webpage the sound effect doesnt play a expected. I tried playing with the dropdownlist of property settings too such as Sound : and theres a dropdown list. I chose chirp.mp3 there but still no luck. Tried some other sync settings too but not able to make this work.