Noise Control Products
Many employers use personal protective equipment (PPE) such as ear plugs or ear muffs to reduce employee exposure to damaging sound as their first line of defense. However, the Occupational Safety and Health Administration (OSHA) states in 29 CFR 1910.95(b)(1) that, “. . . feasible administrative or engineering controls shall be utilized to control employee exposure to high sound levels and PPE should only be used when these controls fail to reduce sound levels below regulatory standards."
Engineering controls are defined as, "Methods of controlling employee exposures by modifying the source or reducing the quantity of contaminants released into the workroom environment" (Fundamentals of Industrial Hygiene, 3rd edition, published by National Safety Council, 1988). Noise control products are used to provide an engineered solution for reducing employee noise exposure. There are some product types you can consider to help implement a noise control plan.
Noise control materials can be cut, shaped and applied to most surfaces. Convoluted Foam Sheets are used when low and mid-range frequency sound absorption is required. These sheets are suited to lining machine surfaces, cabinets, guards, walls, enclosures, ducts, privacy panels, computer rooms and recording studios. Foam Rolls are used when high frequency sound absorption is required and they are ideally suited for lining machine surfaces, cabinets, guards, walls, enclosures, ducts, plenums, housings and sound traps. Quilted Rolls absorb sound similarly to the foam sheets and rolls, and should be used when ASTM-E84 Class I fire performance is desired.
Ready-to-use noise control products are pre-engineered and are designed for easy installation. Wall blankets mount on walls, ceilings and equipment by using grommets and are impervious to dirt, grease and solvents. Steel and fabric panels are a decorative option and mount on any flat surface. Portable screens are good to use in areas when temporary noise reduction is required. Overhead sound baffles and acoustical ceiling tiles are used to reduce reverberations and eliminate sound reflection from the ceiling in environments such as factories, gymnasiums and atriums.
Here are some common terms that are often used when discussing engineering controls to help reduce noise exposure.
Absorbers – Materials used to reduce noise reflection and to dissipate noise energy.
Acoustical Material – Materials used to alter a sound field. The material may be used to absorb, damp or block acoustical energy.
Barriers – Materials used to block transmission of noise.
Damping – The process of dissipating mechanical vibratory energy into heat.
Decibel (dB) – A unit used to measure the power of a signal, such as an electrical signal or sound, relative to some reference level. An increase of ten decibels in the power of a signal is equivalent to increasing its power by a factor of ten. As a measure of sound intensity, a zero-decibel reference is stipulated to be the lowest level audible to the human ear; the speaking voice of most people ranges from 45 to 75 decibels.
Frequency – Pitch or the number of cycles that a sound wave completes per second and is measured in Hertz.
Loudness – Is the subjective human definition of the intensity of a sound.
Noise – Any undesired sound
Noise Reduction Coefficient (NRC) – A scale representation of the amount of sound energy absorbed upon striking a particular surface. An NRC of 0 indicates perfect sound reflection; an NRC of 1 indicates perfect sound absorption.
Sound – Pressure waves that travel through the air or on other elastic materials.
Sound Absorption – The acoustical process whereby sound energy is dissipated as heat rather than reflected back to the environment.
Commonly Asked Questions
Now that this article has introduced some of the basics of noise control a more in-depth exploration of developing a hearing conservation program can be found in Quick Tips article # 260.
Find even more information you can use to help make informed decisions about the regulatory issues you face in your workplace every day. View all Quick Tips Technical Resources at www.grainger.com/quicktips.
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The content in this newsletter is intended for general information purposes only. This publication is not a substitute for review of the applicable government regulations and standards, and should not be construed as legal advice or opinion. Readers with specific compliance questions should refer to the cited regulation or consult with an attorney.
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