Why A vibrating body produces sound but we cannot hear the sound of vibrating pendulum?

Answer 1

Human ears can only hear (i.e., detect vibrations) in a range of about 20-20,000 vibrations per second. A pendulum will usually vibrate at much less than 20 vibrations per second. But please note that a vibrating object (such as a plucked string) may also produce secondary vibrations, other than the main frequency.On the other hand, a vibration must also be strong enough, in order to be heard.

Answer 2

A vibrating body produces sound when it causes air molecules to vibrate, creating sound waves that reach our ears. If the vibrating pendulum is not displacing enough air molecules to create audible sound waves, or if the frequency of its vibrations is outside the range of human hearing, we may not be able to hear it. Additionally, the amplitude and intensity of the vibrations play a role in the audibility of the sound produced.