Question

From an evolutionary standpoint why do ears use fluid pressure waves

Answer 1

The middle ear is the portion of the ear internal to the eardrum, and external to the oval window  of the inner ear. The mammalian middle ear contains three ossicles , which transfers the vibrations of the eardrum into waves in the fluid and membranes of the inner ear. The hollow space of the middle ear has also been called the tympanic cavity, or cavum tympani. The eustachian tube joins the tympanic cavity with the nasal cavity (nasopharynx), allowing pressure to equalize between the middle ear and throat.