First, the sound needs to reach the inner ear somehow. Otherwise we don't hear anything. On its path from a vibrating source the sound can be blocked by obstacles. Which obstacles and conditions can you think of? Do you find more than one?
Okay, acoustic vibrations have reached the delicate structures of the inner ear. Which parts of the inner ear tell your brain that a low tone? What can go wrong here? Can you explain with the model why older people lose high tones first?
The acoustic vibrations do not reach the inner ear. Can you find more than one cause of a conductive hearing loss (1) in the ear model? There are many on the path from the outer ear to the hair cells which translate vibrations into nerve pulses. We chose a very common one, namely a middle ear infection, also called otitis media (2).
The structures of the inner ear have been set into motion, but you don't hear anything. Which reason can you find for sensorineural hearing losses (3)? Damaged or poor cochlear hair cells are the most common cause. They can be damaged by damage genetic mutations or simply by loud noises, like headphones at high volume over time.
What's missing in the model of the inner ear?
Only if you watch the model closely, you will find a nerve fibre attached to the hair cells. Right, also this nerve can be damaged and prevent the transmission nerve pulses to your brain.