t=2π(l/g)^( 1/2)=2π(0.5/9.8)^( 1/2)= 1.42
One minute = = 60 seconds
One cycle is to complete four maximum amplitudes, and one round trip is half a cycle, so in 1 minute, the clock ticks about n times:
n = 60/(T/2)= 120/ 1.42 = 84.5
Considering the initial position, it is reasonable to conclude that the ticking sound is about 84 or 85.