Question

Why do we hear buzzing bees but not pendulum vibrations?

Answer 1

Buzzing bees and pendulum vibrations:

1. Sounds between $20\mathrm{Hz}$ and $20\mathrm{KHz}$ are detectable by the human ear. These are called Audible Sounds.
2. Human ears are incapable of hearing frequencies below $20\mathrm{Hz}$ and over $20\mathrm{KHz}$.
3. Humming bees produce sound by beating their wings, and their frequency ranges from $20\mathrm{Hz}$ to $20000\mathrm{Hz}$, which is audible.
4. The pendulum, on the other hand, produces sound at a frequency of less than $20\mathrm{Hz}$, which is below the audible range, and we don't hear it.