How does iphone cancel sending sound by SMS?

Are you talking about a short sound that sounds like "woo"

That is the default system sound when the iphone edits and sends and receives text messages by itself, and there is no way to eliminate it. I also have my 3GS. Did I use 1 or do I still have it? There is no way to cancel. Unless you mute the phone or set it to vibrate, it's gone.

Even if you escape from prison, you still have this sound, but this sound will only appear when you receive information from others or when you send a message. If the phone is in standby state, or when you are playing iphone, the message you receive is your default "glass" sound.