Final answer:
If the ear canal is blocked, the tympanic membrane vibrates less, reducing the ability to convert sound into mechanical vibrations. This affects the amplification process within the middle ear, as the ossicles need these vibrations to transmit sound effectively.
Step-by-step explanation:
When the ear canal is blocked, such as when wearing earplugs, the direct result is that the tympanic membrane vibrates less vigorously. This reduction in vibration affects the ability of the eardrum to convert sound waves into mechanical vibrations that can be processed by the auditory system. The outer ear, consisting of the pinna and ear canal, functions to funnel sound waves toward the tympanic membrane (eardrum). Once the sound waves reach the tympanic membrane, they cause it to vibrate. These vibrations are necessary for the next step in the hearing process.
The middle ear, which contains the ossicles (malleus, incus, and stapes), amplifies these vibrations. When the ear canal is blocked, the amplification process is hampered, as the ossicles rely on the volitional vibrations of the tympanic membrane to transmit sound. The stapes, in contact with the oval window of the cochlea, transfers these mechanical vibrations into the fluid-filled cochlea. The resulting waves within the cochlear fluid stimulate hair cells, which then convert these mechanical signals into electrical impulses sent to the brain.
In essence, the blockage does not make sounds echo or increase their loudness; it prevents the outer and middle ear from accurately transmitting sounds. Neither does it result in the pinna being unable to collect sounds nor do the ossicles within the ear canal get blocked from moving; it's the transmission of sound to these ossicles that is dampened. Furthermore, the tympanic membrane does not shrink but has restricted movement, which can diminish hearing temporarily, and the sensation can be described as a type of conductive hearing loss. Hearing protection like earplugs is recommended to protect the ear from damage due to exposure to loud sounds, as it preserves the delicate hair cells in the cochlea.