Etymotic ER•200DW8 Personal Noise Dosimeter with Data Logging - Manual (Page 4)

Introduction
Hearing loss from loud sound affects millions of people.
Noise-induced hearing loss is preventable, but most people
don’t know how long they can listen to loud sound without
risking hearing damage. A single noise exposure may not
result in hearing loss, but permanent damage to the inner
ear from noise adds up over time. The accumulation of too
much noise day by day, year after year, is the determining
factor in hearing loss risk. A sound level meter is a device
that measures noise at a particular point in time, while
a dosimeter measures sound levels for many hours and
calculates the cumulative noise dose in percent.
Daily noise dose is determined by both the intensity of the
sound and the amount of exposure time. A 100% dose
means that a person has reached the maximum noise
exposure for the day, and continued exposure to loud sound
could lead to hearing loss. Ideally, hearing protection should
be used before the dose reaches 100% since dose limits are
based on averages, and some ears are more susceptible to
noise damage than others. When the noise dose exceeds
50% a person has reached half the maximum noise exposure
for the day and it’s a good idea to use hearing protection to
prevent over-exposure, particularly if a 50% dose reading is
reached early in the day. Noise dose limits are based on a
5-day work week, and assume quiet during non-work time.
So the noise dose limit per week is 500% (100% x 5 days).
Using hearing protection when dose exceeds 50% reduces
the likelihood of exceeding the limit of 500% dose per week.
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