Have you ever been to a party and your ears are blasting minutes after you have left the venue? Or have even experienced hearing significantly less hours or days after? I hate to break the obvious to you. It probably comes from the way too loud music, that caused you temporary noise related hearing loss. But can noise related hearing loss even be temporary?
Our ear works in not so mysterious ways, it consists roughly of inner, middle and outer ear. Sounds enters through the outer ear, gets to the eardrum which leads vibration to bones (malleus, incus, stapes) located in the middle ear. Those send vibrations to the fluids in the cochlea finally moving hair cells along the membrane. The movement opens the sensory cells on top of the hair cells which creates an electrical signal, that is being carried by the auditory nerves to the brain. The brain converts the signals and recognizes what we know as sound.
During noise related trauma not only the hair cells but also the whole corti may be disrupted. If you assume that this only happens when firecrackers are exploding close to you or you standing right next to the speakers at a rock concert, you are absolutely correct, but noise trauma doesn’t start there. While firework shows may be at 140-160 dBA and concerts roughly at 94-110/120 dBA hearing loss can occur way way before that.
To understand what this means it is important to recognize the meaning of dBA and how it works. Many factors define your experience of sound, this may be endurance, intensity, volume, frequency or the surroundings you’re experiencing it in. There are two very important scales to measure sound which are called “dB” and “dBA”, translated to decibels and A-measured decibels. While dB is solely used to measure sound intensity, dBA also adds the human’s ear response to the intensity. dB and dBA sounds are relatively similar in measuring sounds in the human hearing range. Sounds that the human ear doesn’t respond to such as above and below the human hearing range can be measured in dB. The US Department of Health and Human Servies visualises why measuring in dBA is necessary: “(…) a lower frequency sound that isn’t processed as effectively through the ear will have a lower output level. For instance, the lowest note on a tuba (16Hz) will have a much lower dBA reading than a dB reading.“. However, the by far most important thing to understand about those two scales is that they work logarithmically. This means that if you add 10 dBA to a sound of 80 dBA, the sound will become 10x more intense and twice as loud to our ears, it grows in a steep curve.
To be able to put noise into relation, we must outline at what noise level things are happening; a normal conversation is held at 60 dBA, the maximum volume level for personal listening devices is between 105-110 dBA, standing beside or near sirens equals roughly 120 dBA. That’s quite a range – remember the curve is logarithmical – but what gives another insight what sound does to you is when you put the exposure time into consideration; A rule of thumb is that you are likely to damage your hearing at 85 dBA when you’re exposed to it for minimum 8 hours, at 100 dBA for minimum 14 minutes and at 110 dBA for at least 2 minutes. Clubs and Bars in Macedonia play music at over 110 dBA. We measured the dBA levels in Kotur and Stanica with an app, both were above a 100 dBA at almost every given time during the evening. Considering your hearing can get damaged after roughly 14 minutes of exposure, this is shocking.
There is more than one cause of permanent and non-permanent hearing loss. A very common damage type is for example damages affecting the hair cells. Generally, almost everyone is born with roughly 16000 hair cells. The Center for Disease Control and Prevention states that “Up to 30% to 50% of hair cells can be damaged or destroyed before changes in your hearing can be measured by a hearing test. By the time you notice hearing loss, many hair cells have been destroyed and cannot be repaired.“. This may put you into a stage of alarm but even when hearing less after a concert, it doesn’t necessarily mean your hearing will never go back to its normal state again. You can visualize the hair cells as grass blades bending to sound. While many of those hair cells may recover, continuous exposure of loud noises will over time destroy more and more of those cells. Every single time you listen to overly loud sounds you’re basically putting yourself into a situation of risk.
The best intervention is prevention for this case. There is not much you can do when your hair cells have been destroyed. EPA and WHO recommend keeping environmental noises below 70 dBA in time periods over 24 hours, and below 75 dBA in periods over 8 hours to prevent hearing loss. You could – during your workday for example – take breaks from your headphones or reduce the volume of your music or if you work in a loud working environment make sure to take regular breaks and to not strain your ears after work time. When going to noisy areas there’s also options to protect your ear; this can be for example ear muffs, – plugs,- protection and more.
More than 600 million people of the global population (=12%) are at risk for hearing loss of which 1/3 are connected to noise exposure. Noise related hearing loss is irreversible. Everybody who has the means should try to protect their ears. Your life will simply change when one of your five senses works less. Take responsibility for your health and start to protect your ears, nobody else can be responsible for them.
Centers for Disease Control and Prevention – How does loud noise cause hearing loss?
U.S. Department of Health & Human Services – How is Sound Measuered?
National Library of Medicine – Current insights in noise-induced hearing loss: a literature review of the underlying mechanisms, pathophysiology, aasymmetry, and management options
Healthy Hearing – Smartphone decibel meter apps to measure noise levels
Centers for Disease Control and Prevention – What Noises Cause Hearing Loss?
National Institute on Deafness and Other Communication Disorders – Noise-Induced Hearing Loss
Colonial Center for Hearing – Is Noise-Induced Hearing Loss Irreversible?
The national campaign for better hearing – How loud is too loud?
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