I am a trainer and consultant in lean manufacturing, Six Sigma, quality management, and business management.
What Is a Decibel?
Decibel levels are important because they tell you how loud or quiet a sound is. This is crucial because if a sound is too loud it can damage your hearing permanently. We usually measure how loud sound is through the use of a measure called the decibel, one decibel being one-tenth of a bel, a very infrequently used measure. It is a measure of the sound pressure level or loudness.
The decibel scale is not a linear scale, it is a logarithmic scale. A doubling of your decibel reading does not mean a doubling of the noise—for every 10dB increase in sound our perception of loudness doubles. So 60dB is twice as loud as 50dB and 70dB is four times as loud as 50dB.
How Loud Is Loud?
Below is an illustration of decibels against common sounds that most people are familiar with to try to help you understand the decibel scale. What most people think of as loud is anything above about 80dB which is the sound of an alarm clock. Normal speech is around 60dB to 70dB.
At 85dB most people can suffer hearing damage from prolonged exposure, it is recommended that you are not exposed to 85dB for more than 8 hours in any one day. When the sound gets to around 120dB you have reached the pain threshold for most people and immediate damage to your hearing is possible.
Sound vs. Noise
When we talk about noise and sound what do we mean? A sound is a vibration that we pick up via our eardrums; the strength of which we can measure using decibels. But how is sound different from noise...or is it?
A noise is just an unwanted sound, in some cases what you perceive as being noise others perceive as being a pleasant sound such as the differences in opinions that my daughter and I have regarding what is on the stereo! One person's noise is another person's preferred listening.
However, we also use noise to indicate that not only is a sound unwanted but that it is usually too loud. We use noise to describe a sound that is louder than we are comfortable with, often so uncomfortable that it could potentially cause damage to our hearing.
Noise is a very real hazard in many workplaces and noise-induced hearing loss is something that you have to seriously protect yourself against. I have worked in factories where there are hundreds of presses in operation stamping out panels for car parts; the noise in these factories is such that you feel every stroke of the big machines as well as hear them. Even with quality hearing protection you can still hear and feel the noise within the factory. You would certainly suffer severe hearing loss if you operated these machines without protection.
Noise-Induced Hearing Loss
Noise-induced hearing loss is what occurs if you are exposed to noise that is too loud for too long. Noise is a vibration and if those vibrations are too big and powerful they can cause severe damage to our eardrums; even rupture them.
In an industrial setting occupational health and safety regulations require the use of hearing protection if the average sound level is 85dB or more as well as a host of other requirements such as annual hearing tests to assess noise-induced hearing damage.
This means that you will need to get equipment to measure the sound levels within your workplace and use hearing protection to protect your hearing and the hearing of your employees.
Many people think that they don't need to use hearing protection at home, but it is just as important as using it within an industrial setting. Hearing loss can happen at home just as easily as work if you expose yourself to high levels of sound for prolonged periods.
Having worked within press shops with 1000-ton presses in operation, I would recommend the full earmuff style ear protection shown here rather than the plugs that you insert into your ears if you really want to protect your hearing.
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How Much Noise Can We Endure?
Everyone's hearing is slightly different and as with many things, people's endurance and ability to withstand damage vary considerably. However, the table below gives guidance as to how long someone can safely be exposed to sound levels.
|Noise Level (dBA)||Maximum Exposure Time in 24 Hours|
130 to 140
less than 1 second
Measuring Decibel Levels
Measuring how loud something is can be done quite cheaply and easily with simple tools that are available today. You can even download apps to your phone for measuring decibel levels, however, these would not be very accurate and should only be used for "fun."
The decibel meters available online are not that expensive however if you are looking for one to monitor your workplace ensure that you purchase one that meets the requirements of legislation as some are very basic. That being said you will still not have to spend more than a hundred bucks!
If you have any doubts at all about whether your work environment is too noisy you should get a meter such as the simple one shown here and measure the noise levels. Better to measure and monitor your decibel levels than to ignore them and get hit with a lawsuit later on from an employee who has suffered hearing damage. Ignorance is no protection in a court of law.
Protecting Your Hearing From High Decibel Levels
In environments where you are exposed to noise above 85dB it is advisable to wear hearing protection to prevent hearing loss. If you know the level of noise that you will experience then you can choose hearing protection that will reduce the sound to less than 85dB.
Earplugs and earmuffs have decibel ratings as to how much they can reduce sound levels by, so for instance a pair of earmuffs may reduce sound at the ear by 25dB so it would be OK to wear these in an environment that has average decibel readings of 100dB but would not be advisable to wear them where sounds reach 120dB as they would not provide enough protection.
Wearing too strong a hearing protection device in lower noise environments can also cause problems as you would not be able to hear what people have to say or even shouted warnings; so wear the right hearing protection for the right environment.
If you are concerned about decibel levels wear ear protection to ensure that you save your hearing.
Correctly Wearing Hearing Protection
Far too often as a manager in noisy work environments I have found employees wearing ear protectors incorrectly. They push back earmuffs from their ears to leave their ears exposed or fail to fully insert plugs. They often claim that they need to hear their colleagues.
The problem is that they can still sue you if they then develop hearing loss even though they have taken it upon themselves to not use the provided protection correctly. It is vital that you police the use of hearing protection thoroughly as not everyone realizes or believes how easy it is to damage hearing.
The other thing is to consider the types of hearing protection that is being provided. We sometimes provide ear muffs and ear plugs that are too efficient for the levels of noise in our work. You should compare the ratings of the protection that you provide against the actual decibel levels of your environment to ensure that you don't make it impossible for your operators to hear each other or even the machines. Remember you only have to bring the level down to below 85dB, so if your noise levels are 95dB then you need hearing protection that will cut out 10dB.
© 2012 Tony
Alex from UK on March 26, 2014:
Well written hub, perhaps worth mentioning the difference between a meter which gives a spot measurement and a dose meter. When working in places where the noise level is low but varies it is hard to judge whether exposure is a problem unless you get dose measurement.