First try adjusting the volume control on your Nintendo DSi.
Check whether this problem only occurs when playing a certain game or if it occurs with all games.
If the problem only occurs with one game check whether the volume can be turned off via the game's options menu and if this function has been activated. If this does not solve the problem, the game will need to be returned to Nintendo Australia for inspection/repair.
If the problem occurs with all games, the Nintendo DSi will need to be returned to Nintendo Australia for inspection/repair.
NOTE: We can only perform repairs or replacements exclusively on games that are published and distributed by Nintendo Australia.