| To measure the loudness of sound, a unit of | | | | for an eight-hour workday has become a standard in |
| measurement called a decibel (dB) is used. A decibel is | | | | the mining, construction, oil-gas well drilling, and |
| one tenth of a bel (B), or the unit of measurement | | | | agriculture industries, as well as the U.S. Air Force and |
| devised by engineers of the Bell Telephone Laboratory | | | | Army. Loss of hearing caused by excessively loud or |
| to quantify the level of sound reduction when a tone is | | | | prolonged noises is called NIHL, or noise induced |
| transmitted over one mile (1.6 km) of standard | | | | hearing loss. |
| telephone cable. Since the bel proved to be too large | | | | Injury to the cilia cells |
| for most common sound measurements, the use of | | | | Sounds of less than 80 dB do not often result in |
| the smaller decibel became more popular. | | | | hearing loss, even after long or repetitive exposure. It is |
| The decibel is used in a wide variety of scientific | | | | not possible to predict how an individual will respond to |
| measurements related to acoustics and and | | | | loud noises, since each person possesses a different |
| electronics. This unit of measurement places a physical | | | | hearing sensitivity. Yet, exposure to a single loud noise |
| value - usually of noise or light intensity - in which a | | | | or continuous noise exposure can result in temporary |
| doubling of actual intensity causes perceived intensity | | | | hearing loss. This temporary loss is known as |
| to always increase by roughly the same amount. | | | | temporary threshold shift, and it will typically resolve 16 |
| Specifically, a 3 dB increase is about equal to an | | | | to 48 hours after the end of exposure. |
| approximate doubling of sound. This is important to | | | | Hearing loss can be permanent if the offending sound |
| understand because when you look at the dB values | | | | is loud enough to damage or destroy the delicate inner |
| given in the following charts and text, you will | | | | ear cells, called cilia, or stereocilia, that are found in the |
| understand a relatively small numerical increase of 10 | | | | cochlea of the inner ear. These cilia cells respond to |
| dB between the sound of rainfall and a sewing | | | | mechanical sound vibrations by sending an electrical |
| machine accounts for the significantly greater noise | | | | signal to the auditory nerve. The mechanism of injury |
| level. It also shows that the 110dB sound of a | | | | to cilia is purely physical; excessive vibration results in |
| screaming child is only several times less intense than | | | | microscopic tearing or breaking of the cilia. There are |
| a thunderclap or a rock concert. | | | | many cilia located in the cochlea of the ear; the more |
| Sound reference chart | | | | that are damaged, the more profound the deafness. |
| 0 Rustling leaves | | | | Once cilia cells are chemically or physically damaged |
| 20 Ticking watch | | | | or destroyed, they will not regenerate or repair |
| 30 Quiet whisper | | | | themselves. |
| 40 Refrigerator hum | | | | Protect your hearing |
| 50 Rainfall | | | | A commonsense recommendation to avoid hearing |
| 60 Sewing machine, typical conversation level speech | | | | loss due to excessively loud noise is to either wear |
| 70 Washing machine | | | | hearing protection or remove yourself from the sound |
| 80 Alarm clock (two feet away) | | | | source. |
| 85 Average traffic | | | | Use either earplugs, earmuffs or other protection |
| 90 Gas lawnmower | | | | devices when exposed to sounds above 85 dB. Since |
| 95 MRI testing | | | | you cannot always be certain when your sound |
| 100 Tractor, hair dryer, subway train | | | | environment places you at risk, use this rule of thumb: If |
| 105 Power mower, chainsaw | | | | you are talking to someone three away from you and |
| 110 Screaming child | | | | you cannot clearly hear what is being said, the noise |
| 120 Rock concert, ambulance, thunderclap | | | | level around you could be damaging your hearing. |
| 130 Jackhammer, jet engine plane (100 feet away) | | | | Do the obvious, and simply walk away when sounds |
| 140 Fireworks | | | | are too loud or turn down the volume of the sound |
| 165 12 gauge shotgun blast | | | | source if possible. It is also possible to limit the sound |
| Noise in the workplace | | | | intensity by not standing directly near its source. Time |
| The National Institute for Occupational Safety and | | | | spent in a loud environment is important to the health |
| Health (NIOSH), a branch of the U. S. Centers for | | | | of your hearing, so limit the time you expose your ears |
| Disease Control and Prevention, reports that ear injury | | | | to loud noises. Cover your ears with your hands or |
| can develop in workers if exposed to 85 dB or more | | | | cross the street when you hear someone operating a |
| over eight hours. As a result, this 85 dB exposure limit | | | | leaf blower or when you are near a jackhammer. |