You are right, I misread the Update notification.
There are three locations where Push notifications are configured
a) Settings; Notifications; Facebook
"Notification Center" must be switched "ON"
"Alert Style" must be set to either "Banners" or "Alerts"
"Badge App Icon" must be set to "ON"
"Sounds" must be set to "ON"
"View in Lock Screen" must be set to "ON"
b) Settings; Facebook; Settings
"Vibrate" must be set to "ON"
"Play Sound" must be set to "ON"
c) Within the Facebook app
Open the Settings page, select Notifications and check that all check marks that you need are set.
I am not sure, but could it be that you can have Facebook Notifications only on one iOS device, so that if you have Facebook both on iPad and iPhone only one will show push notifications?
If you have done all these steps and still receive no sounds when Push Notifications appear, it is safe to assume that the problem is not on your end.
regards, Chris