Wirelessly posted (htc Pocket PC: Opera/9.5 (Microsoft Windows; PPC; Opera Mobi/15954; U; en))
Well, if you are constantly using something on your device when you get a call, text, or email you are going to hear the notification tones to let you know you recieved a message or a call.
That's what is supposed to happen.
If you don't want to hear the alert sounds for events then disable or change the sounds or set certain events to vibrate in Sounds and Notifications.
From the Start Menu go to Settings/Personal Tab/Sounds and Notifications.