Bells - for the quarter hours? (there's a short sequence that you should get once for xx:15, twice for xx:30, thrice for xx:45 and four times at xx:00 followed by xx bongs to tell you which hour). And of course church clocks are not always *right* so getting the xx:15 chimes at xx:20 wouldn't be all the surprising. During the day there might be different sequences for "we are about to start a service in this church" (which might be a daily mass or might be a wedding or funeral), in the evening bells get rung for "bell ringers need practice at this".

And yes, with all the church-bell noise you'd think people'd be able to cope with a call to prayer or five.