I'm not that smart.
But some phones have SD cards, some don't.
And if I write an app on the phone with the SD card, the path to the file is different do the phone with no SD card.
So if possible I'd prefer to not rely on that as the way to do things.
But I don't mind using system directories.
I'm sure all phones would have a "music" or "sounds" directory.
So - I could put a directory in that called "effects" (or notifications) and manually put the files there before installing the app.
But I'm still finding my way around phone directories.