Hearing loss reduces our ability to hear, and to a greater or lesser degree it can be mild, moderate or severe. Either way, preventing hearing loss, and treating it promptly if it has already occurred, is the best way to stop it from progressing further, as well as stimulating the ear and supporting the cognitive side of the brain.
It’s worth distinguishing hearing loss from deafness. Deafness occurs when there’s no longer any perception of sound through the ear or ears, whereas with hearing loss, sound is still perceived, but depending on the degree of loss, it will be heard at higher or lower decibels depending on the frequency. This makes it much harder to hold a conversation, understand what other people are saying, and hear certain sounds that are no longer perceptible to the ear itself, to the point where it’s easy to forget we could once hear them.
Types of hearing loss
Depending on which part of the ear is affected, hearing loss is classed as conductive, sensorineural, or mixed.
Conductive hearing loss: affects the middle ear, while the inner ear remains in perfect condition. The damage can involve the ossicular chain, the eardrum, the round window, the Eustachian tube, or the outer ear canal. Any problem with these middle ear structures prevents sound from reaching the hair cells of the inner ear.
Sensorineural hearing loss: the hearing problem lies in the inner ear, and can affect the cochlea, the auditory nerve, or one of the pathways leading to the brain’s cortex. The middle ear works fine, since its structures aren’t damaged and it can transmit sound, but once it reaches the inner ear, due to damage to some of its structures, the sound isn’t detected.
Mixed hearing loss: mixed loss has the distinctive feature of being a combination of conductive and sensorineural loss.
According to this scientific article, central hearing loss and functional hearing loss also exist. Central hearing loss relates to the brainstem — a clear example is when a person hears, but doesn’t understand what’s being said to them.
As for functional hearing loss, this refers to non-organic hearing loss, which can be either voluntary or involuntary.
Hearing loss scale
To determine what type of hearing loss a patient has, we use the following scale:
As we can see in the chart above, normal hearing falls between 0-20dB. Mild hearing loss starts between 20-40dB. From this point on, hearing aids should be considered, since moderate loss begins around 40dB and goes up to 70dB. Severe loss falls between 70-90dB, and we talk about profound loss once we go past 90dB.
In all cases, to a greater or lesser extent, hearing loss also affects speech understanding, especially in noisy environments where we have to focus our hearing to understand what’s being said.
Hearing aids by type of hearing loss
Once the hearing loss is known, the hearing care specialist is the one who chooses the most suitable hearing aid, taking into account the patient’s needs and preferences.
There are different types of hearing aids:
RITE or miniRITE (receiver in the ear): these sit behind the ear, with the microphone also positioned there, above the auricle. The ear canal stays open, so sound reaches it naturally. They’re small in size, since the receiver, connected to the hearing aid, runs externally straight into the ear canal as a thin wire, together with a micro-dome or tip that’s inserted into the ear. Recommended for mild to moderate hearing loss, as long as low frequencies are preserved, avoiding occlusion.
BTE (Behind the ear): as the name suggests, this type sits behind the ear. It’s on the larger side, since it houses all its components inside, including the receiver, which is also why it can offer more advanced technology. To carry sound to the ear, it usually has a tube, which can be thinner or thicker, and a custom-made mould that seals the ear canal and holds it in place. It’s usually prescribed for severe hearing loss.
POWER (high power hearing aid): these are the largest hearing aids available, and also sit behind the ear. They have a thicker tube to carry sound to the ear, together with a custom-made mould. They’re designed for profound hearing loss, and being more powerful, they also offer greater amplification.
Next, there are in-the-canal hearing aids, all custom-made to fit the patient’s ear canal, although none of these are suitable for people with excessive earwax or a very narrow ear canal. They’re small, but also offer fewer features, since all the electronic components have to fit in that limited space. There are three types of in-the-canal hearing aids: half-shell (HS), in-the-canal (ITC), and completely-in-the-canal (CIC).
HS (half shell): known as “half-shell” hearing aids, custom-made to fit the ear. Of all the custom-made hearing aids, this is the largest, as it also fills the ear bowl (concha). Recommended for mild to severe hearing loss.
ITC (in the canal): called “in the canal” because it’s inserted into the ear canal, although the faceplate of the hearing aid, where the battery compartment and volume control are located, remains visible. This type of hearing aid is prescribed for mild to moderate/severe hearing loss.
CIC (completely in the canal): of all the in-the-canal hearing aids, these are the smallest and most invisible, since they sit completely inside the ear canal. Also recommended for mild to moderate hearing loss.
References
https://www.nidcd.nih.gov/es/espanol/perdida-de-audicion-en-los-adultos-mayores (Spanish)
LIBRO-BLANCO-SOBRE-DISCAPACIDAD-AUDITIVA-HELIX-Ámbitos-de-actuación, recursos, ayudas y protocolos. Federación de Asociaciones por la integración del Sordo en la Comunidad Valenciana. (Spanish)
