Final answer:
In bone conduction testing, sound bypasses the outer and middle ear structures, directly stimulating the cochlea via vibrations through the skull. This method is useful in diagnosing and assisting with conductive hearing loss, where typical sound transmission through the ear.
Step-by-step explanation:
In bone conduction testing, the signal effectively bypasses the outer and middle ear structures, which include the auricle, or pinna, and the ossicles (malleus, incus, and stapes).
Typically, these structures conduct sound vibrations from the external environment through the ear canal to ultimately stimulate the inner ear.
However, with bone conduction, vibrations are sent directly through the skull to the cochlea, circumventing the ossicles entirely.
The process of hearing involves the vibration of the tympanic membrane (eardrum) triggered by sound waves, which is then passed to the ossicles of the middle ear.
The malleus (hammer) connects to the tympanic membrane and transfers the vibrations to the incus (anvil), which in turn passes them to the stapes (stirrup).
From the stapes, the vibrations move to the oval window and into the cochlea, where they generate waves in the cochlear fluid.
This motion stimulates tiny hair cells that convert the mechanical vibrations into neural signals.
However, in situations of conductive hearing loss, where there may be damage to the ossicles or blockage in the ear canal, bone conduction can be used as a method to still stimulate the cochlea.
For instance, hearing aids designed for bone conduction press against the bone behind the ear, directly driving vibrations to the inner ear.
Similarly, tuning fork tests like the Rinne and Weber tests help in differentiating between conductive and sensorineural hearing loss using bone conduction principles.