phone whilstles or bell rings: sounds on Samsung Galaxy S3 I have two very basic questions about my Samsung Galaxy S3 phone. In its
default configuration:


Every now and then the phone whistles. (a) What does this mean?
(b) How do I change this or turn it off permanently?
A few months ago the operating system did an OTA (over-the-air) update.
Now every now and then, besides this whistling, I also hear a bicycle bell
ringing. (a) What does this mean and how does this differ from the whistling,
that is, how is the information conveyed by the whistling different by the
information conveyed by the bicycle bell ringing? (b) How do I change this
sound or turn it off altogether permanently?


Thanks.
These are both notifications. To change them or even just find out what they are notifying you about go to Settings > My Device > Sound
You can change the "Default Notification Sound" (even choosing silent, but then you won't get any notification sounds) and a little bit lower on the menu you can set distinct defaults for specific samsung apps. There are many apps that allow you to choose different notifications sounds (other than the default that you chose above), but those have to be changed in the apps themselves. 

Do you notice any new information in the notification area (by swiping down from the top of the screen) when you hear these alerts?