Ask everyone a physics question.

Cowhide rocket launchers have a good vibration effect. If soldiers sleep as pillows at night, they can hear the hooves of enemy soldiers dozens of miles away to prevent sneak attack.

If the enemy attacks at night, the sound will spread through the solid (ground), and soldiers can know in advance and prepare for the battle through the well-vibrated cowhide quiver.

Bone conduction: the sound is transmitted to the auditory nerve through the skull and jaw, and the way of sound transmission that causes hearing is called bone conduction.

Note: Normal people hear other people's voices through the vibration of the eardrum, through the ossicles, and hear their own voices mainly through the skull. It is for this reason that listening to the recording of your own speech is different from listening to your own voice directly.