3M X3A Manual

3M Ikke kategoriseret X3A

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United States Canada

Technical Service 1 800 243-4630 Technical Service 1 800 267-4414

Sales Assistance 1 800 896-4223 Sales Assistance 1 800 265-1840 ext. 6137

G12

2000 Resource Guide

Hearing Protection

Education

How to Use

the Noise

Reduction

Rating (NRR)

The NRR describes the average

sound level reduction (attenuation)

provided by a hearing protection

device (HPD) in a laboratory test.

Since the NRR is based on

laboratory testing, it does not take

into account the loss of protection

that occurs when hearing protectors

are not fit properly or when they are

not worn for the entire time that the

wearer is exposed to noise

For most wearers, the NRR

identified on the current EPA label

(shown here) significantly

overestimates the protection of the

hearing protector in the workplace.

This rating is based on an

“experimenter fit” method of

measuring HPD attenuation.

Using the EPA Noise Reduction

Rating (Experimenter Fit)

The NRR on the EPA label

shown to the right is based on the

average amount of attenuation

provided by an HPD when it is

worn by 10 different people during

a laboratory test. During this test,

the person conducting the test fits

the hearing protector on each

person. This “experimenter fit”

method results in ratings as high as

33 dB. Since research indicates

that these ratings overestimate the

protection that many wearers will

receive in the real world, 3M

RECOMMENDS REDUCING

THE NRR before attempting to

estimate the effectiveness of an

HPD as follows:

1. Subtract 7 dB from the NRR if

noise is measured on the A-

weighted decibel scale (dBA).

(Skip this step if noise is measured

on the C-weighted dB scale)

2. Divide the result of step 1 (NRR-

7) by 2. This is known as

“derating”.

A New Rating: NRR (SF)

A new “subject fit” method of

measuring HPD attenuation will be

used in the future to calculate a

different rating; the NRR (SF). The

people (subjects) in this laboratory

test fit their own protector according

to the manufacturer’s instructions

without the help of the person

conducting the test. Compared to

the NRR shown on the current EPA

label, the NRR (SF) is usually a

lower rating that may be closer to the

performance of the hearing protector

An Example of Reducing the NRR

8-hour TWA noise exposure: 93 dBA

NRR of hearing protectors: 29 dB

Subtract 7 dB from the NRR: 29 dB - 7 dB = 22 dB

Divide by 2: 22 ÷ 2 = 11 dB

Subtract 11 dB from the

8-hour TWA noise exposure: 93 dBA - 11 dB = 82 dB

Decide if 82 dB (known as the “Protected Exposure”)

is below the PEL for noise

in the real world. For more

information about the NRR (SF),

contact 3M Technical Service at

800 243-4630.

Estimating Noise Reduction for

Individual Users

The labeled values of noise

reduction are

based on

laboratory

tests. It is not

possible to

use these data

to reliably

predict levels

of protection

achieved by a

given

individual in

a particular

environment.

To ensure

protection, those wearing hearing

protectors for occupational

exposures must be enrolled in a

hearing conservation program. Non-

occupational users should have a

hearing evaluation by an audiologist,

physician, or other qualified

professional, on a regular basis.

Produkt Specifikationer

Mærke:	3M
Kategori:	Ikke kategoriseret
Model:	X3A
Produktfarve:	Black, Red
Materiale:	Plastic, Stainless steel, Thermoplastic polyurethane (TPU)
Bæremåde:	Headset
Anbefalet alder:	Voksen
Dielektrisk hovedbånd:	Ja
Støjreduktionsforbedring (NRR):	33 dB