A vibrating object causes air molecules to vibrate. When these vibrations reach our ears, they are collected by the pinnae and funnelled into the ear tube. These vibrations strike the eardrum, which starts to vibrate at the same frequency. This causes the delicate bones of the middle ear to vibrate. This stimulates tiny hair in the hearing organ that sends a signal to the auditory nerve of our nervous system. The auditory nerve takes the signal to the brain and we can hear the sound.