Hearing aids replace the cochlea and the essential apparatuses contained within. Most significantly, they perform the role of the receptor cells lining the basilar membrane within the cochlea, which are responsible for the transduction of information carried by physical energy into electrical energy within the nervous system. This type of hearing aid is of value to an individual suffering from conduction deafness, which is deafness brought about due to damage to the apparatuses of the ear. An example of this would be a soldier deafened by exploding ordinance, or an airport worker continuously exposed to the loud volume of plane engines without sufficient ear protection. Cortical deafness, also known as nerve or sensorineural deafness, however, is brought about through damage to the auditory regions of the nervous system. As such, an individual with perfectly healthy ears might be rendered deaf due to damage caused by a stroke or brain trauma. This kind of deafness cannot be rectified by hearing aids, or any other form of extant medical intervention. "Ossicle" may refer to the bones of the inner ears (the auditory ossicles), but is not itself the name for a form of deafness nor is "auditory."

The pinna is the formal term for the body part that is commonly referred to as the 'ear'. This is the portion of the ear that projects from the head. This is the first point of contact with air vibrations that will enter the ear canal to pass their vibrations onto the eardrum. The tympanic membrane the formal term for the eardrum. From here, the auditory ossicles are vibrated. These are the three, minute bones found within the middle ear: the malleus, incus, and stapes. These three bones transmit the vibrations onto the oval window of the cochlea, which contains the basilar membrane, where transduction of the physical information occurs.

Thus the correct order is: pinna, tympanic membrane, auditory ossicles, and cochlea.

The frequency of a vibration corresponds to the pitch of the perceived sound produced from it. Higher frequencies will produce higher pitched notes, while lower frequencies will produce lower pitched notes. On the other hand, the amplitude of a sound wave will determine the volume of a perceived sound. Timbre is a complex component of a sound, and is the result of a variety of other elements. To provide a brief illustration however, timbre explains why a G# note on a trumpet sounds distinct from a G# note played on a piano. The longevity of a note is not the result of either the frequency or the amplitude of a sound. This is simply determined by how long the vibration continues.

The frequency of a sound wave, or the pace of its vibrations within the ear, will determine the sound's pitch. The sound's loudness is determined by the amplitude of the sound wave, the timbre by its complexity.

Sensorineural hearing loss is permanent and often results from the loss or damage to hair cells or the nerve from the ear to the brain. For this reason, it occurs from damage to the inner ear, where the nerve and hair cells are located. Damage to the middle ear would result in conductive hearing loss. Damage to the outer ear, would likely result in decreased sound localization. 

Sound waves are pressure changes and loudness is related to the amplitude of the wave. It is quantified by the decibel (dB). Pascal is the standard unit for pressure. Whereas, Hertz is used to quantify frequencies and an octave is a doubling in frequency. Meters/second describes the speed at which sound propagates.