What directly activates the receptors of the auditory analyzer?

this is fluid vibrations in the cochlea.
Contact receptors are excited by direct contact with a source of irritation. Auditory receptors (phonoreceptors) belong to mechanoreceptors, are secondary and are represented by internal and external hair cells that are located on the main membrane inside the inner ear. Sound vibrations that occur in the air are transmitted through the external auditory canal, the eardrum and the chain of auditory ossicles to the vestibular window of the labyrinth, causing wave-like movements of the perilymph, which, propagating, are transmitted to the spiral organ and excite receptors.