On occasions, you may find that the audible tone that is used by Safari to indicate to VoiceOver users that a webpage is loading may continue to play after the page has fully loaded. On these occasions, the tone will typically continue to play if you switch away from Safari to another app or to the Home screen.
Steps to reproduce
There appears to be no reliable means of reproducing this behaviour, although it does appear to be more likely to occur if you navigate away from Safari before the webpage does fully load. However, on these occasions, if you then return to Safari, you will find that the page has fully loaded. Even now, the tone will still continue to play.
The tone can be stopped by either double-tapping on the ‘Reload’ button in Safari or by toggling VoiceOver off and back on again.