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How Loud is Too Loud?

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This isn’t quite as easy to answer as you might think. If you have a teenage son, for example, you may have experienced the discrepancy between what you think constitutes too loud (‘100 Ways to Hate’ by Five Finger Death Punch screeching out of his Bluetooth speaker) and what he thinks constitutes too loud (you whispering, “Come on, son, time to get up. School day.”).

As a rule of thumb, any noise you have to shout over in order to be heard should be considered too loud. This kind of noise will generally be around 90 decibels (dB). The Control of Noise at Work Regulations 2005 (the Noise Regulations) from the Health and Safety Executive requires that employers must provide hearing protection to their employees where noise exceeds 85dB. And workers must never be exposed to noise above 87dB (factoring in reductions due to ear defenders etc). [1]

85dB is roughly the equivalent to the sound of a diesel truck driving past at 40mph around 50 feet from where you’re standing. In other words, the kind of noise that’s likely to make you suspend your conversation until the commotion has passed. If you were to stand a similar distance from a jet taking off, you’d experience approximately 150dB of noise. This would almost certainly rupture your eardrums.

If you’re wondering why a difference of just 65dB has taken you from having to raise your voice to excruciating pain and hospitalisation, it’s because every 10dB increase in sound is experienced by the human ear as a doubling of volume. So, a jet plane taking off is more than 64 times louder than a passing truck. To clarify: an increase from 40db to 50dB is twice as loud (10dB equals x2); but from 40dB to 70dB is eight times as loud (30dB equals 2x2x2). This is a very important point of consideration from a safety point of view, as the uninitiated is likely to think that exposing their ears to 100dB is only a little worse than 90dB, where it is, in fact, twice as harmful!

How the Ear Hears

To understand how loud is too loud, and why certain levels of sound are harmful or even dangerous, we need to know how the human ear works.

Anatomy of the Human Ear

It’s a common misconception that what we experience as voices or music or noise are essentially signals sent to the brain in response to sound vibrations striking the eardrum. It’s actually a little more complicated than that.

Here’s what happens:

  • Sound waves (for example, ‘100 Ways to Hate’ by Five Finger Death Punch) enter the ear canal and strike the tympanic membrane (also known as the eardrum).
  • These vibrations pass through the tympanic membrane and into the bones of the middle ear, called ossicles.
  • The vibrations move through these ossicles in the following order: the malleus (hammer), the incus (anvil) and the stapes (stirrup).
  • As well as moving through this system of tiny bones (the smallest in the human body), the vibrations are also amplified 22 times greater than when they entered the ear.
  • The final bone in this sequence, the stapes, transmits vibrations to the fenestra ovalis (or ‘oval window’) on the outside of the cochlea, a spiral–shaped cavity filled with a thin liquid (perilymph).
  • The perilymph moves in response to the sound vibrations.
  • The cochlea contains the ‘organ of Corti’ which features hair cells tipped with tiny projections called stereocilia. These hairs and stereocilia move in response to the motion of the perilymph.
  • By a process known as auditory transduction, the organ of Corti sends electrochemical impulses (known as action potentials) corresponding to the original sound vibrations through the auditory nerve to the auditory cortex.
  • Congratulations, you’re now listening to ‘100 Ways to Hate’ by Five Finger Death Punch!

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How Loud Noise can Damage Your Hearing

Except for the fleshy bits that stick out of the sides of your head (the pinna) everything else that comprises the ear is very, very delicate. As we stated earlier, the roar of a jet engine in close proximity creates 150dB of noise (128 times louder than a diesel truck) which is more than capable of rupturing your eardrum.

A ruptured eardrum is an extremely painful experience but shouldn’t in itself lead to deafness. Provided there are no complications, a ruptured eardrum can heal itself in about six weeks to two months, although some surgery may be required.

Noise Induced Hearing Loss (NIHL) is actually caused by damage to the delicate hairs in the cochlea. A loud noise can cause these hairs to flatten down (permanently or temporarily) or even break. Once broken, these hairs do not grow back. Most people have at some time subjected themselves to a temporary flattening of these hairs. For example, after a rock concert, a raucous football match or a loud nightclub, you might have experienced a ‘dulling’ of your hearing. It probably sounded as if you were underwater. Depending on the extent of the damage, this may have lasted anything from an hour or so to a couple of days.

Damage to these hairs can not only cause partial or complete deafness, it can also result in tinnitus. Tinnitus is commonly experienced as a ‘ringing in the ears’ but it can also manifest as hissing, clicking, whistling or swooshing. However it manifest, it is not only debilitating because it interferes with your ability to hear but also because it can lead to insomnia, depression and anxiety.

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It isn’t just sudden loud noises that can result in NIHL. Prolonged exposure to lower decibel levels can have a damaging effect, too. In fact, the majority of cases of NIHL in the UK (of which there are an estimated 18,000!) are likely to be caused by long-term exposure to noises of around 80dB for eight hour periods.

How do you know if you’re hearing is being compromised or damaged?

Any noise which you have to shout above in order to be heard will be damaging your hearing. Any noise which causes discomfort or pain will be significantly damaging your hearing. Signs that your hearing has been damaged include:

  • muffled hearing (as if you’re underwater)
  • ringing in the ears (tinnitus)
  • conversation becomes difficult
    • You keep asking people to speak up
    • People keep accusing you of not paying attention
  • you have to turn up the TV volume

If you are experiencing any of the above symptoms, you should make an appointment to see your GP and also assess your home environment, workplace and lifestyle to identify and rectify the issues that may be resulting in inner ear damage.

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Summary

  • Avoid exposure to sounds above 85dB unless you are wearing the appropriate ear defenders.
  • Avoid continued exposure to noises between 80dB and 84dB
  • Be on the lookout (hearout?) for the initial symptoms of hearing loss

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[1] http://www.hse.gov.uk/noise/regulations.htm

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