Mechanism of hearing:

The pinna collects sound waves and
impinges on the tympanic membrane which vibrates accordingly. These vibrations are transmitted by the three ear ossicles (malleus, incus, and stapes) to the oval window. This results in a displacement of fluid in the middle canal. At this point, sensory stimulation takes place, movement of the basilar membrane distorts the sensory cells of the organ of corti. This results in impulses being fired to the brain through the auditory nerves.

Path of sound vibration from the pinna to the inner ear

The sound vibration picked by the pinna passes through the external auditory canal to the external auditory canal to the ear drum (tympanic membrane). The vibration of the ear drum is then picked by the middle ear (consisting of malleus/hammer, incus and stapes) where it the passes to the oval window magnified causing vibration of the round window which passes the vibration to the perilymph and then to  the endolymph.