Question

Why does not produce sound when it osscilates?

Answer 1

I believe you are talking about the oscillation of a pendulum.

If something vibrates at a frequency of, or in between 20Hz to 20KHz, we can hear it. Otherwise we can’t. Because our ear can hear only this frequency range. This is known as the audible frequency range.

OK, now according to this question the oscillation of pendulum is lees than the 20Hz(that is, the swing of a pendulum isn’t grater than the 20 times in 1 second ).

That’s why we can’t hear the sound of pendulum oscillation.