Hallo Michael,
es gab einmal in einem anderem Forum dieses Problem:

Since we upgraded to a new iSeries with V5R2, our applications don't make any sounds anymore. For example, when entering an order and there is not enough inventory, it used to beep along with displaying the error message. I can't get it to beep anymore even though I have the correct sound settings in Client Access.
This question posed on 06 January 2004

Answer:

There is a PTF for this: SI03077. Download and install it and your sound will be back.

Das SI03077 wurde ersetzt durch das SI14295. Ist dies nun
angelegt oder nicht auf dem Pc bzw. AS/400 ?