how to reset push notifiction setting

[arthur5011]

hi all, need some advice on push notification testing.

we develop an app with push notification feature, but when we install on to our test device, the result on each device are varies

result:
iPad 2, iOS 5.0.1 - received successfully
iPhone 4S, iOS 5 - failed to received any notifications
iPhone 4S, iOS 5.0.1 - failed to received any notifications
iPhone 4, iOS 5 - failed to received any notifications
iPhone 4, iOS 4.3.3 - failed to received any notifications
iPhone 4, iOS 4.3.5 - received successfully
iPhone 4, iOS 4.3.1 - received successfully

for those devices that failed to received notification, i have perform below troubleshooting:
1st:
1. delete app & provisioning profile installed by the app.
2. reboot > reinstall app > launch app

2nd:
1. delete app & provisioning profile installed by the app.
2. reboot
3. change date to future date > reboot
4. reinstall app > launch app

and lastly, another question: can we by default disable the sound when we send the notification from our push notification portal?

thanks,
arthur