High sound levels, or what we often call “noise”, can permanently damage hearing.  There are several ways that hearing loss can be prevented, whether it’s at work or during recreation.  For example:

• Choose quieter equipment, or retrofit machinery with noise dampening devices.
• Install engineering controls like sound barriers or enclosures to reduce noise exposure.
• Reduce the amount of time that each individual is exposed to noise.
• Apply electronic technology like active noise cancellation.
• Use hearing protectors such as earplugs or ear muffs.

Safety wisdom and experience have taught us that hearing protectors should be used as a last resort.  Inadequate protection can result from choosing the wrong type of hearing protector, improper fit, not wearing or inserting it properly, or not wearing it often enough (or at all !).  However, other forms of hearing protection can be difficult to apply properly so, in practice, hearing protectors are a very common choice.  If you’re going to be using them to prevent hearing loss, you should start by choosing the right hearing protector for your noise environment.

“It is possible to calculate the reduction of the protection as a function of the “off time”.  In some cases, this reduction can be as high as 95% or more if the protectors are removed for as little as three or four minutes.”

CSA Standard Z94.2-02

CSA, the Canadian Standards Association, has published an excellent standard to help make the right choice.  CSA Z94.2-02, “Hearing Protection Devices – Performance, Selection, Care and Use” is a comprehensive guide on hearing protectors.  The standard has been adopted in occupational health and safety legislation in many regions, including Alberta’s Occupational Health and Safety Code.  Earplugs, earmuffs, communication headsets and helmets equipped with earmuffs are included in Z94.2-02.

Among the many technical details in the standard are three methods of selecting hearing protectors.  There are two important prerequisites before these methods can be used:

1. The manufacturer must measure the attenuation (noise reduction) of the hearing protector, and publish the prescribed information on its packaging.
2. The user needs noise exposure data.  For some methods, these must be time-weighted exposure measurements, not just spot readings at selected locations.

The three selection methods described in Z94.2-02 are:

·       Grading or Classification,

·       Single Number Rating (SNR), and

·       Octave Band Computation.

A brief comparison of these methods is shown in Table 1 below.

Grading is generally considered to be the simplest method of choosing hearing protectors.  Using exposure data from the noise environment, choose the appropriate grade of hearing protector as shown in Table 2 below.  Grades or classes of each hearing protector should be found on the manufacturer’s packaging.

* L_ex,8: Equivalent noise exposure over an 8-hour period, measured in A-weighted decibels

A careful choice of hearing protectors is one of many important factors in minimizing hearing loss.  Consult the references below for more information.

Useful References

1. “Five Important Things You Should Know About Noise Exposure”, article published on Guzzardi and Associates website, www.guzzardiassociatesohc.com

2. CSA Z94.2-02, “Hearing Protection Devices – Performance, Selection, Care and Use”, Canadian Standards Association, www.csa.ca

3. Noise Control in Industry: A Basic Guide, Canadian Centre for Occupational Health & Safety, 1999