Updated: Oct 9, 2021
The most common type of hearing loss is sensorineural (approximately 90% of hearing loss cases) and is experienced after the age of 55.
Sensorineural loss is attributed to the cochlea (inner ear), which is our organ of hearing.
This organ is spiral shaped and contains a long membrane bathed in fluid. Sounds (vibration of air molecules) are delivered to the membrane of the cochlea via the ear canal, eardrum and middle ear bones. The membrane then moves along its length, and tiny ‘hair cells’ amplify and translate the vibration movements to electrical signals that the brain interprets as sound.
At the beginning of this membrane is your high frequency (pitch)hearing area, and as you travel the length of it, the pitch it relates to gets lower and lower. The beginning is where wear and tear damage first starts to accumulate, so people begin with a high frequency hearing loss. This progressively gets worse, and starts to affect lower frequencies too. Although it is felt after 55, it starts happening earlier in adulthood. It isn’t an issue earlier as it is not speech that’s impacted. This is why some children can hear dog whistles, but after the teenage years pretty much no one can.
Hair cells that should be amplifying sound and transmitting it to the auditory nerve are damaged and lost. Currently we cannot regenerate these cells and therefore the loss is permanent. The effect of this is that sounds need to be louder before we are able to detect them.
Speech sounds such as F, Sh, S and Th are the first to be impacted because they are quiet and high pitched/sharp. This results in a loss of speech clarity because although you still hear the overall words, some of the sounds are absent. Losing the ability to hear sharp sounds gives the effect of people ‘mumbling’ when they speak. Speech and environmental sounds are dull. Words are mistaken because the clarity is missing. Fish could be fist or thrift. Three thirty becomes two thirty, and communication is difficult as vital words are misheard and lost.
At first, you manage with your hearing loss. As long as people are close by and speaking directly to you, you get enough volume to interpret the words. If someone turns away or moves a few steps back, the intensity of their speech is reduced/drops below your threshold. Background noise presents an even bigger problem. With normal hearing you can interpret speech that is just a few decibels (like the difference between volume 10 and volume 11 on your TV) above the level of the noise. When you are hard of hearing, you need speech to be considerably louder than the noise in order to follow the conversation. In restaurants or supermarkets therefore, the hearing loss makes it difficult to distinguish words and the person can start to ‘tune out’ of the chatter at social gatherings because they are finding it tiring and difficult.
Sensorineural loss typically affects not just the threshold at which you can detect sounds, but also the intensity of sound. On a hearing test you might not hear anything below 85dB (loudness of a lawnmower, say) at a high frequency such as 8kHz. But when you hear a 90dB sound you’ll perceive it as being quiet, the same intensity as a whisper.
As hearing loss gets progressively worse more speech sounds such as K and P are affected, and things like birdsong and the beeping sounds of chip and pin devices are now totally lost. Typically, a person with sensorineural ‘wear and tear’ loss will still have very good low pitched hearing; in fact they may not be aware of their problem because they can still hear a car door closing halfway down the street from their front room. Vowel sounds will still be easy to hear. Arguments can erupt with your wife - she tells you to do something about your hearing and gets “I’d hear you fine if you stopped mumbling” in return.
Children and women’s voices are the most difficult to hear, as they are higher pitched than men’s. Sadly this can mean that young grandchildren are difficult to understand, and family gatherings require patience on all sides while the hard of hearing person asks for family to repeat words. Over time, the husband or wife learns to speak louder/shout to avoid repeating words.
Because you often aren’t aware of speech you missed, it is difficult to know the impact on others. Your husband called you from the lounge twice, then came through to the kitchen and asked you again. Unless he tells you this, you don’t know you’re hearing it for the third time when he speaks in the kitchen.
Blame is often placed on sound quality. Sensorineural loss makes good quality TV sound poor quality, and if the sound is poor quality to start with, it’s impossible. This is why we hear BBC news easily but struggle with ITV dramas and American films.
When hearing loss has progressed enough to affect middle frequency words, the hard of hearing person can no longer deny there’s a problem. Sensorineural loss worsens very gradually, and it’s not unusual for people to wait 5 years from first noticing to getting help. Hearing aids are currently the only way to treat this type of hearing loss, and they are better, smaller, more natural-sounding than ever before. I believe strongly that everyone has a cut off point. They have to reach a point where they are struggling *enough* because no one wants hearing aids! They can be fiddly and you need to tolerate new sounds . So a person has an internal cost:benefit ratio. The benefit is hearing aids restore easy conversation and environmental stimulation/connection. Phone calls are less tiring and embarrassing, conversations around the home are easy even when the person is behind you or has their head in the cupboard. The cost is sometimes literal (private aids cost between £500-£4500) but also hassle and effort to rehabilitate with new ‘bionic ears’!
Your hearing loss, in my opinion, tends to affect other people first. Family will be frustrated by the communication difficulties. If they perceive you to be avoiding having a hearing test, they may be annoyed because it’s a fixable problem. They will speak up and support you when you’re out, they will repeat what the cashier said, they’ll maybe make phone calls for you. You are having a hard time but likely there are others around you having a hard time compensating for the hearing loss too.
I very often find that the husband/wife/children of my patient triggered the hearing appointment because “I think I’m managing just fine!”. But the good news is that even though they were frustrated (and have been for a few years!), they will also be delighted when you take the first step towards hearing better - and so will you once you give it a go!
I’ll write next about hearing aids and how they work, along with rehabilitation support from your audiologist.