I’m often asked about safe sound levels, and I’ve found an excellent and easy to read guide to sound levels, exposure times and hearing damage here.
After having this discussion with a musician recently, I decided to share my thoughts. Hearing damage can occur without any changes to your hearing test results, so it’s possible to damage your ears and still get a normal test result.
Typically, noise damage shows up on hearing tests as high-frequency hearing loss, with the worst loss at 4kHz and a recovery at 8kHz. This gives a classic “tick” on the audiogram like the one below:
But more recent studies have found that loud noise exposure damages hearing in several different ways. Immediately after a rock concert, for example, there is a drop in hearing ability. This is known as a temporary threshold shift (TTS) when the structures in the ear have been damaged, but can recover over a couple of days. So you would see a drop on your hearing test but it would come back to normal. In animals, it has been seen that repeated TTS leads to a greater than expected age related hearing loss later on. So although you recover your hearing by Monday morning, if you keep going to the nightclub every Saturday without ear plugs you can expect to be wearing hearing aids sooner and have a greater degree of hearing loss in later life.
Noise exposure causes metabolic damage in the inner ear and brain over the 7 or so days following the exposure. Long after the hearing has returned to normal, there is hidden damage. Repeated exposures increase the severity of the damage. We now know that synaptopathy is one result of noise exposure. What this means is the the structures in the inner ear may be ok, but the nerves and the communication between brain cells is impacted.
This hidden damage may not show up on the hearing test, but it means a person can have difficulty interpreting speech in background noise. Even in relatively quiet situations like a family dinner, it can be a struggle to work out what people are saying. When in an echoing environment or one with background music and lots of people, it becomes even more difficult.
This can be interpreted incorrectly by both the patient and the audiologist. You may be told you have a ‘mild’ hearing loss, and therefore hearing aids are not prescribed, or you don’t want to have them. When I assess hearing, I consider speech in noise difficulties along with the test results. You should be led by the reported difficulty levels as well as the test.
Both the hidden and the obvious hearing damage from noise can be helped with technology. When a person has great difficulty distinguishing speech in noise, a more advanced technology is required to help them. By using sound processing along with directional microphones, we can improve the “signal to noise ratio” ( the speaker’s voice versus the background hubbub) by some way. It’s never perfect but it’s a fantastic help. If you’re struggling but you’ve been told by the NHS that your hearing isn’t bad enough for hearing aids, get a second opinion!
In terms of preventing this damage in the first place, we have also come a long way:
1) You can download an app to measure sound levels wherever you are.
2) Working conditions and hearing protection are taken seriously.
3) Hearing protection has improved greatly. Custom made noise filters are available that protect from noise damage while allowing clear sound in. These are particularly useful for musicians as they retain the quality of the music, versus earplugs that dampen every frequency.
4) Cheap, foam earplugs are readily available from chemists/Amazon and very easy to use.
5) Children and teens are more aware of noise damage than ever before, with smartphones calculating/reducing unsafe sound levels.
6) Noise-cancelling headphones are available, meaning you don’t have to turn up the input level just to offset the surrounding sounds.
I’m hopeful that we will eradicate noise induced loss for this generation onwards, but I’m there for those who already suffer hearing loss and tinnitus from past exposure. The most important takeaway from this is that it’s never too late to protect your hearing. Hearing is precious and even if you did damage in the past you must look after what you have now.
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