Dangerous+Decibles

=**__Decibels__**= The **decibel** (**dB**) is a logarithmic unit that indicates the ratio of a physical quantity (usually power or intensity) relative to a specified or implied reference level. A ratio in decibels is ten times the logarithm to base 10 of the ratio of two power quantities. A decibel (dB) is one tenth of a bel (B), i.e., 1B = 10dB. The bel represents a ratio between two power quantities of 10:1, and a ratio between two field quantities of 10:1. The decibel is commonly used in acoustics to quantify sound levels relative to a 0 dB reference which has been defined as a sound pressure level of .0002 microbar, or 20 micropascals.
 * Noise induced hearing loss (NIHL) is hearing loss due to a sudden loud or sharp noise above 85 decibels.**

=**__What can be heard by the human ear?__**=
 * A man with normal hearing can actually hear 0 decibels. 0 decibels is similar to a mosquito buzzing about 3 metres away. At about 110 decibels a person would begin to feel pain from the noise; protection should be worn well before this level.**

The human ear is divided into three parts: the Outer Ear the Middle Ear and the Inner ear. Sound waves are collected by the visible part of the outer ear, focused through the ear canal where it is filtered to the Cochlea. The cochlea is filled with fluid whose capacity is a fraction of a drop. This is where the pressure from a sound wave is changed into an electrical current that the brain is able to read and process. When hearing loss occurs, it its typically gradual and without warning over a lifetime, this is not to say that aging causes hearing loss, constant exposure to loud sounds is typically the root cause. Although in certian instances sudden exposure to a loud sound can cause permanent damage

The Human ear can pick up an extremely wide range of sounds from 0 decibels (db) though 120 db which is considered the "Threshold of Pain." Some common sounds and their everyday db rating are as follows. 10db, Insect noises at night, open field 40db, Subdued conversation 50db, Average office 60db, Average conversation 70db, Busy street 90db, Heavy truck traffic; baby crying; trombone, 16 inches away 96db, Jack hammer 110db, Electric guitar amp at maximum volume, 6 inches away 140db, Inside a bass drum, airport runway 150db, Permanent damage to hearing 160db, Jet engine, close up 180db, Rocket engines 220db, 12 feet in front of a cannon below the muzzle.

media type="youtube" key="nd5CyNyzasQ" height="315" width="420"

So for most people, around 90 decibels would be enough to cause a headache and possible permanent damage. =**__What is the official level of sound in which you need to start wearing ear protection?__**= media type="youtube" key="MjdVP9hIaa4" height="315" width="420" align="center"


 * **The reference to the 24-hour period is meant to protect those employees who may work more than 8 hours within that time period. For example, if an employee starts his shift at 8 am, ends at 4 pm, then comes back to duty at midnight for another 8-hour shift, that employee shall be considered to have worked for 16 hours within that 24-hour period. In that case, the employee's noise exposure level (Lex, 8) shall not exceed 84 dBA over a 16-hour period (as opposed to the limit of 87 dBA over an 8-hour period).**
 * **Even though the Schedule starts at an A-weighted sound pressure level of 87 dBA and ends at 120 dBA, it is incumbent upon the employer to take into consideration all noise from at least 74 dBA onwards as per subsections 7.2(3) and (4).**
 * Paragraphs 7.7(1)(//a//) and (//b//) prescribe that when an employer is required to make a report to a regional health and safety officer as referred to in section 7.6, the employer shall provide a hearing protector to every employee whose exposure is likely to exceed the maximum permitted levels prescribed in subsection 7.4(1).**
 * It should be noted that the use of hearing protection is considered the last line of defence to protect the hearing of workers. If an employee's exposure to noise is in excess of 87 dBA ( Lex, 8 ), or exceeds the limits in the Schedule, and cannot be reduced by administrative or engineering controls or other physical means, in a reasonably practicable manner, the use of hearing protection is mandatory.**
 * " -Canadian Occupational Health and Safety Manual**
 * " -Canadian Occupational Health and Safety Manual**

So, according to Canadian Law, if you are exposed to noise levels over about 87 decibels, you should not be exposed for more than eight hours. If you are in a work environment of more than 84 decibels, you should not be exposed for more than sixteen hours. Hearing protection is mandatory in any environment where the noise level is that of 87 decibels or higher.


 * Sarah D.**

[] [] [] [] [] []