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HEARING PROTECTION INFORMATION
DRO-AUDIO PRODUCTS
Noise exposures that are loud enough and last long enough could damage the nerves in the inner ear complex system that will result in
permanent and irreversible hearing loss. Repeated exposure to noise levels above 85dBA or one exposure to 140dBA could results in
hearing loss. The hearing disability is gradual, has no warning signals and is accelerated with age. By using the correct ear protector all
the time whilst exposed to the danger workers can reduce the effect of gradual hearing loss.
Due to the complexities of measuring noise pollution and the gradual nature of hearing
loss it is highly advisable that work areas be measured by a professional to determine
the risk and recommend the correct noise reduction required. The loudness sensitivity
of the ear for tones is not the same as the ears damage risk for noise.
There are various methods of rating the effectiveness of hearing protectors. The selected method for Dro-Audio products is the SNR
(Simple or Single Noise Reduction Rating) as used by the European Union and affiliated countries. The Hearing protector is tested in
accordance with ISO 4869-2 (Testing with experienced users and a frequency rage from 63 Hz to 8000 Hz). These results are
calculated and interpreted into a single noise reduction (SNR) as well as into three general bands of the noise spectrum, H=high
frequency, M=medium frequency & L=low frequencies: SNR 30 (H=36, M=27, L=18)
When using the SNR information be aware of the various scales of measurement for noise:
A-Weighting (dBA)
Replicates the frequency sensitivity of the ear at low levels. Most commonly used weighting scale as the
method predicts the damage risk to the ear quite accurately.
B-Weighting (dBB)
Replicates the frequency sensitivity of the ear at moderate levels and is mainly used to predict
performance of audio appliances such as loudspeakers.
C-Weighting (dBC)
Replicates the frequency sensitivity of the ear at very high noise levels. As this scale is quite flat, the
scale will include a lot more of the low frequency range than that of the B & C scales.
Many hearing Occupational Health and Safety Acts rely on the dBC (C weighting) however most of the actual industrial measurements
are based on the bBA (A weighting) and this could lead to specifying the incorrect hearing protector. As a guideline to correct the
discrepancies of the two different scales weightings the following is the accepted guideline:
Noise level
Hearing Protector
Protected Noise Level
90 dBC
23 dB
67 dB
90 dBA
23 dB – 7dB (Correction Factor for error)
74 dB
EN 458, a European guidance document that gives hearing protector recommendations, suggests selecting hearing protection devises
that reduce the level of exposure to the ear to between 70 and 85 decibels A-weighted sound level (dBA). If a protector with too high
an SNR attenuates noise to below 70 dBA, the wearer also is overprotected and is at risk of missing key alarms and instructions.
EAR PLUGS · EN 352-2
MIDI PLUG ~ DUAL FLANGE (RE-USEABLE) 19 SNR
Each pair individually packed in re-useable bags.
400 per bag & 10 bags per carton (4000 ear plugs)
MIDI-P
MIDI-PC
UN-CORDED
CORDED
EAR MUFFS · EN 352-1
JUNIOR MUFF (UNIVERSAL)
J-M
28 SNR in Red or Blue
48 per carton (individually hanger packed)
BIG MUFF
BM
30 SNR in Red or Blue
48 per carton (individually hanger packed)
CLASSIC EXTREME MUFF
CEM
30 SNR (HF) in Blue only
15 per carton (individually box packed)
MEASURMENT IN dB
H
M
L
SNR
HIGH
MEDIUM
LOW
SINGLE
MIDI EAR PLUGS
EN 352-2
20
16
15
19
JUNIOR MUFF
EN 352-1
28
21
13
24
BIG MUFF
EN 352-1
33
27
18
30
CLASSIC EXTREME MUFF
EN 352-1
36
27
18
30
MAKE THE RIGHT CHOICE?