Question

Why do we hear the sound produced by the humming bees while shound of vibrations of a simple pendulum is not heard

Answer 1

It is because Human Ear has audible range nearly 20 - 20000 Hz .
The vibrations of the simple pendulum has frequency <20 Hz .
Whereas frequency of sound produced by humming bees are in audible range .
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hope it helps!

Answer 2

The audible range of frequency for humans : 20 Hz to 20 kHz

The frequency of sound produced by humming beings is in the audible range that humans can hear.

The vibrations of the Pendulum  have frequency less than 20 Hz , which cannot be heard by humans.Sound waves with frequency less than 20 Hz is called infra sound.

Thus ,  we hear the sound produced by the humming bees while sound of vibrations of a simple pendulum is not heard