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Glossary of Terms for Hearing Protection |
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ANSI |
American National Standards Institute
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Attenuation |
The amount of noise that is absorbed or repelled by a hearing protector.
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"A" Weighting |
This scale corresponds to the way the human ear hears across the common frequencies (reported in dBA). The emphasis is on the human ear (real ear).
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| "C" Weighting |
Provides a flat frequency response with slight attenuation of the very high and very low frequencies (reported in dBC), also called an octave band analysis. The emphasis is on machinery frequency analysis.
Note: To convert “C” weighting noise to “A” weighting noise a simple 7 rule applies.
i.e.: “C” weighting (dBC) - 7 dB = “A” weighting (dBA)
All hearing protectors are rated in the “A” weighting scale i.e. dBA.
In South African noise regulation legislation, “A” weighting noise is used (dBA).
Example:
Noise measurement 107 dBA
Hearing protection attenuation 30 dBA
Noise after protection 77 dBA
Safety Act requirement below 85 dBA
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CE Mark |
The CE mark is a symbol of conformity on industrial safety products that have been approved for sale in the European Union (EU).
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| Continues Noise |
The intervals of the sound waves are less than one second apart.
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Decibel - dB |
A unit used to measure the intensity of a sound or the power level of an electrical signal by comparing it with a given level on a logarithmic scale.
In general use, a degree of loudness.
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Derating |
In South Africa we generally do not derate the attenuation of hearing protection products.
If the products are approved by recognized standards (i.e. EN - European, ANSI - American, SABS - South African) and the product suppliers offer recognized hearing conservation training, it should not be necessary to derate the products.
Uvex only offers product that is EN approved. The SABS follows the EN (European) standard.
South African legislation requires that hearing conservation training is carried out annually for all users.
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Exchange Rate |
The rate at which sound energy is averaged over time. Utilising a decibel scale, every time the sound energy doubles, the measured level increases by 3 dB. This is the 3 dB exchange rate that most of the world uses.
In the U.S., OSHA uses the 5 dB exchange rate.
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Frequency |
Represents the number of cycles of vibration that occur in one second. The number of cycles is designated in Hertz (Hz). This is perceived as “pitch.”
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Impulsive Noise |
The intervals of the sound waves are greater than one second apart and are characterized by a high-amplitude, very short wave.
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Linear Sound |
A sound that is a consistently flat response throughout the measured frequency range.
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Mean Attenuation |
The average attenuation value calculated received in each test frequency.
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NHCA |
National Hearing Conservation Association
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NIHL |
Noise Induced Hearing Loss due to noise exposure.
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NIOSH |
National Institute for Occupational Safety and Health.
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OSHA |
Occupational Safety and Health Administration
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PHP |
ersonal Hearing Protection
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Presbycusis |
Type of sensory neural hearing loss due to aging.
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PTS |
Permanent Threshold Shift refers to a permanent change in hearing thresholds due to noise exposure.
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SLC80 |
The Australian standard for testing hearing protection products.
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Sound Level Meter |
An instrument used for the measurement of sound level. It consists of a microphone, a frequency selective amplifier and an indicator. It measures sound level in dB SPL.
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Standards |
All uvex products conform to the European hearing standard EN 352 and the South African Bureau of Standards SABS 50352.
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Rating |
NRR vs SNR Definitions
There are two rating systems that measure the amount of protection a hearing protector will afford to a user.
SNR – Single Number Rating
This was established by the European Union and is aligned with the EN standard in Europe.
NRR – Noise Reduction Rate
This was established by the (EPA) Environmental Protection Agency and is aligned with the ANSI standard which is American.
There is no direct conversion but a reasonably accurate guide is as follows:-
NRR + 2 or 3 = SNR Example NRR 22 = ±SNR 25
South Africa, as with most products generally, follow the European EN standard. Therefore the market prefers the SNR rating.
The following is a full definition of the two ratings:-
SNR - Single Number Rating
Is a rating system set up by the European Union (EU). Tests are conducted by independent testing laboratories with no direct participation by manufacturers. The independent testing laboratories meet all of the regulatory requirements as set out by the EU. The test results serve as a guideline to indicate the amount of potential protection a hearing protection device will give in a noisy environment. All uvex hearing protection devices are tested according to the requirements established under EN 352.2 (ear plugs) and EN 352.1 (ear muffs). All tests are performed at independent testing laboratories located at either B.I.A. Germany, or by Inspec Laboratories LTD, England at the University of Salford, Department of Acoustics.
NRR - Noise Reduction Rating
Is a rating system set up by the Environmental Protection Agency (EPA) as a guideline that indicates the amount of potential protection a hearing protection device will give in a noisy environment. All testing is performed in a controlled environment.
Consequently, posted NRR ratings are a qualified example of how the individual products compare with other similar hearing protection products in an uncontrolled noise environment. Test results do not evaluate the product reusability, comfort, adaptability or quality. In the final analysis, the user must make this determination.independent testing laboratories located at either B.I.A. Germany, or by Inspec Laboratories LTD, England at the University of Salford, Department of Acoustics.
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Tinnitus |
Presence of ringing, buzzing or humming in the ear which can be intermittent or continuous.
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TTS |
Temporary Threshold Shifts refers to a temporary change in hearing thresholds due to noise exposure.
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TWA |
Time Weighted Average. The average of the sampled sound over an eight-hour period.
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Weighting |
Response networks which encompass the frequency range of human hearing ( 10 Hz to 20K Hz ).
“A,” “C” and Linear are the common weighting networks available.
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The Ear Elements |
External Ear
Consists of the Pinna or the visible portion of the ear and the external auditory canal.
Pinna
The visible, outer portion of the ear, which should be enclosed completely by ear muff cups.
Middle Ear
Includes ear drum and ossicular chain (malleus, incus and stapes).
Inner Ear
Cochlea, semicircular canals and auditory nerve. |
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