Not sure... but here are a few thoughts:
If you are doing a Thread.sleep() in between sound playing, make sure that it's happening on a different thread than the main UI thread, since you don't want the UI to freeze up while it's waiting.
Or, (better?), you may want to schedule something to run at a point of time in the future (e.g. more like event-based programming, where an event will be created in the future that triggers some code.)
See some of the examples here, including the 2nd answer using the Handler.postDelayed method, which is Android-specific: https://stackoverflow.com/questions/6205210/is-this-how-to-schedule-a-java-method-to-run-1-second-later