.
Every 9*2*2*5*2 = 360 seconds the bales will ring together.
(360 is LCM = Least Common Multiple of the numbers 9, 6, 4, 10 and 8).
There are 10 360-seconds intervals in one hour,
so the bales will ring 11 times during one hour, if to count starting from the time moment they rang for the first time together.