Once sound waves reach your eardrum (also called the tympanic membrane), they cause it to vibrate. But these vibrations are still too weak to be useful to your inner ear. That’s where your middle ear comes in. This is a small air-filled chamber that is designed to increase the volume of sound with incredible efficiency.
The three smallest bones in the human body:
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Malleus (hammer) - attached directly to the eardrum
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Incus (anvil) - connects the malleus to the stapes
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Stapes (stirrup) - transmits vibrations to the inner ear
Collectively known as the ossicles, these bones work like a mechanical amplifier. They take the relatively low-energy vibrations from the eardrum and amplify them by changing them into stronger pressure waves. This is important because the next part of the journey, that is the inner ear, is actually filled with fluid, not air, surprisingly, and sound energy travels very differently through liquid.
The boost provided by the ossicles increases sound pressure by over 20 times before it reaches the oval window of the cochlea, which is a major part in the basics of how our hearing works. Without this mechanism, you would lose nearly 99% of the sound energy in the transition from air to fluid.
In order to prevent damage from overly loud sounds, like for example, at concerts or quick, unexpected sounds like a shutting door. This tiny muscle, called the stapedius, can tighten and reduce the movement of the stapes. This reflex, called the acoustic reflex, helps protect your inner ear from sudden spikes in volume.
So, while they’re only a bit bigger than grains of rice, these bones are vital. If damaged or stiffened (as in the condition of otosclerosis), the ability to hear clearly, especially lower frequencies, can be affected.