Hearing loss affects a large number of people in the UK and around the world – more than 1.5 Billion!
Did you know there are different types of hearing loss?
Surprisingly, hearing loss is not a one-size-fits-all problem. In fact, there are different types of hearing loss, each with its unique causes and varying degrees of impact on a person’s life.
In this article, we will outline and briefly explain different types of hearing loss, their causes and the different levels of hearing loss that people experience.
There are three types of hearing loss:
- Sensorineural hearing loss
- Conductive hearing loss
- Mixed hearing loss
Each is different. Before we explain each one, it is important to have a basic understanding of how sound gets from our ears to our brain. This is called auditory transduction.
Sound can reach our brains via two routes – Air conduction and Bone conduction.
In Air conduction, sound enters the outer ear and is transmitted along the auditory pathway.
Bone Conduction, on the other hand, involves the vibrations of our skull bones stimulating the cochlea, the sensory organ of hearing.
Air conduction and bone conduction lead to the same stimulation in the cochlea (hearing organ), which are converted into neural impulses.
Now let’s delve into the types of hearing loss.
Sensorineural hearing loss:
This type of hearing loss involves the sensory and neural components of our hearing system.
The sensory aspect of hearing loss is located in the cochlea and occurs when the tiny hair cells that detect sound in the ear are injured, diseased, do not work correctly, or have died.
The neural aspect occurs when there is a problem with the central auditory nervous system.
These types of losses often intertwine, making it difficult to distinguish whether the loss is entirely sensory, neural or a combination of both, so we refer to these types of losses as sensorineural.
Causes of Sensorineural hearing loss vary greatly, including:
- Ageing (presbyacucis)
- Childhood infections, e.g. meningitis, mumps, and measles
- Ménière’s disease
- Regular exposure to loud noises (such as from work or recreation)
- Use of certain (ototoxic) medicines
- Acoustic neuroma
Conductive hearing loss:
Conductive hearing loss happens when there’s a mechanical problem or blockage in the outer or middle ear.
This could be due to improper conduction of sound by the ossicles (small bones behind your eardrum) or the eardrum not vibrating in response to sound.
Potential causes can include:
- Cerumen (wax) build up in the ear canal.
- A foreign object stuck in the ear canal.
- Damage to the ossicles or other moving parts of the middle ear.
- Fluid build up behind the tympanic membrane.
- Perforation of the tympanic membrane.
- Scarring on the tympanic membrane from repeated infections.
- Current infection/active discharge.
Mixed hearing loss:
A person can have conditions leading to both conductive and sensorineural loss, resulting in mixed hearing loss.
This means that not only is the sound blocked from entering the cochlea, but also structures within the cochlea or Central Auditory Nervous System (CANS) aren’t functioning correctly.
Although these are the true descriptors, hearing loss is often described in other ways as well:
Congenital hearing loss:
This refers to hearing loss present at birth, or that develops before the acquisition of speech and language skills.
Congenital hearing loss is one of the most common birth defects in developed countries, with one in 1000 newborns being diagnosed with bilateral sensorineural hearing loss (SNHL) ≥40 dBHL (decibels Hearing Level). There’s also an equal number of children who develop hearing loss before adulthood (Fortnum et al., 2001).
Causes may be hereditary or due to environmental damage and can result in conductive, mixed, or SNHL.
Acquired hearing loss:
As the name suggests, acquired hearing loss appears after birth, and the causes can lead to hearing loss at any age.
Noise-induced hearing loss:
Caused by occupational, recreational or the result of acoustic trauma (e.g. accident, bomb blast), this can lead to temporary or permanent threshold shifts in hearing.
Noise-induced temporary threshold shift:
This follows exposure to a high level of noise, causing an immediate dullness in hearing and possible tinnitus. Complete recovery may take several hours.
It should be taken as a warning sign that repeated exposure could lead to permanent threshold shift.
Understanding Hearing Loss Through Audiograms
Hearing loss impacts people differently, with severity varying from person to person. Typically, it’s measured in decibels of hearing loss (dbHL) using pure tone audiometry (PTA), with results recorded on an audiogram. An audiogram provides us with a valuable visual tool to illustrate the different levels of hearing loss.
Our first audiogram represents varying levels of hearing loss, from normal to moderate and profound loss. Each person’s sensitivity to sound, or the volume they can hear things at, is recorded in dbHL.
If you have a normal hearing level, you can hear a range of sounds at low volume, less than or equal to 20 dbHL, across the full range of frequencies.
On this audiogram, you can see how the patient hears different frequencies. They hear low-frequency sounds like background noise well, but as the frequencies increase to where speech is commonly heard, their ability starts to decline. This graphical representation helps us understand the patient’s unique hearing profile, setting the stage for personalised care.
Hearing Clarity and Speech
The second audiogram adds another layer to this picture, overlaying speech sounds and environmental noises. It illustrates how specific hearing losses can impact the clarity of speech and the recognition of different sounds around us.
Frequencies at which men and women speak often differ, contributing to distinct hearing experiences. Men’s voices typically fall around 1500 to 3000 hertz, whereas women’s speech ranges from 2000 to 6000 hertz.
Mid to high-frequency hearing loss can also compromise the clarity of speech. Key consonant sounds such as “k”, “ch”, “t”, “s”, carry a lot of the meaning in our speech. Without these, speech may become muffled and difficult to understand, especially in noisy environments.
Audiograms provide us with a clear picture of an individual’s unique hearing profile, including their sensitivity to different frequencies. Understanding this range of hearing levels at different frequencies assists us in identifying the best approach for each patient. Ultimately, it’s about enhancing the clarity of sounds that patients may struggle with and ensuring they can engage fully in the world around them.
In conclusion, though hearing loss can be complex to diagnose and challenging to live with, most types can be managed with the right pathway of care, hearing solutions, and rehabilitation. People with hearing loss can lead a completely normal life with the correct assistance and interventions. At Novus Health, we’re committed to helping you along this journey.