Iphone presentLocalNotificationNow不会在后台应用程序时触发警报和声音

I have an App registers for location updates, running tests, sometime when I enter a region while the app is in the background I receive a alarm notification with sound. sometime I only see the notification in notification center, and i did not receive any sound and alert... What can you do to always get the sound and the alert notification ?I have an App registers for location updates, r