What is sound? What is noise?

Simply stated, sound is everything we hear; noise is unwanted sound. Both sound and noise are created by some vibration that generates variations in air pressure that move through the air and finally reach our ears. The person who hears the sound interprets it as wanted or unwanted. For instance, the sound of a jet engine may be music to the ears of a pilot, but a disruptive noise to owners of residential property on the flight path.

Whether we call these variations in air pressure sound or noise, we will undoubtedly pay a high cost if we do not reduce the sources of noise and protect ourselves from its slow degenerative effect on our hearing.

Types of Noise

A continuous noise is constant and stable, such as the endless hum of fluorescent lights or a diesel generator. Variable noise is any noise that changes pitch and volume such as a siren. Intermittent noise is a burst of sound, such as an electric saw being used for a minute or two every 10 minutes or so at a construction site. Impulsive noise comes in short bursts of less than one second such as a hammer hitting a nail or the sound of a starter's pistol at a track meet.

The Impact of Noise

The main impact of continuous exposure to noise is either total or partial hearing loss. Noise also interferes with speech communication and leads to misunderstanding of instructions, distracts the mind from work requiring concentration, and causes stress that, in turn, causes employee inefficiency. Research indicates that continuous exposure to noise may lead to hypertension, changes in blood pressure, heart beat, breathing and sleeping problems, and in some instances a deterioration of mental health. When a person is startled by a loud noise, the breathing pattern changes and muscles tense.

Lack of Understanding

To be heard, your voice must be louder than the background noise. In most social situations individuals address each other at a distance of 2 to 4 meters at a 55-60 decibel (db) level. Thus, to hear a person speaking the background noise level reaching the listener's ear should not exceed 50 db. Communication is possible for a short time if the noise exceeds 78 db; prolonged communication, however, becomes stressful if the background noise exceeds 78 db. Measurement of workplace noise compared to quiet life situations shows the day-to-day dangers of hearing loss for employees:

1. A hand-held circular saw at a 1 meter distance generates 115 decibels.
2. A diesel truck, 85 kilometers per hour at 20 meters generates 85 decibels.
3. A gasoline lawnmower at 1 meter generates 95 decibels.
4. An air compressor at 3 meters generates 120 decibels.
5. A normal conversation at 2 to 4 meters generates 55 decibels.
6. A typical office environment without canned music generates approximately 40 decibels.
7. Determining what is “too loud” may seem at first blush somewhat subjective, but a few tell-tale signs that your workplace may have noise issues include:
   • Do staff members constantly have to raise their voices to be heard?
   • Have any employees complained about a “ringing in their ears” after a long day?
   • Do employees raise their voices excessively when on the telephone?

If the noise level seems to be a problem, find the source and duration of the noise, measure its level in decibels, identify the individual(s) exposed, and, of course, find the steps needed to be taken to reduce noise.

Hire a Consultant

Many new techniques, materials and devices are available to reduce noise at the source and protect the ears. A noise abatement consultant can give your workplace a noise abatement analysis. The consultant may suggest making changes to wall configurations and other internal structures, setting up sound barriers, or purchasing new equipment with a lower decibel rating. Unfortunately, carrying out such suggestions may require a major capital injection into the business. Over the long haul, however, it is in management's best interest to reduce overall noise at its source and protect not only the workers but also ensure that neighbours are not disturbed by high or rising noise levels.

Regardless of when and what structural changes are made, most job sites will still expose workers to noise. Workers should be educated about the long-term hearing loss that will inevitably come if they don't protect their hearing at all times. As an absolute minimum workers exposed to continuous or sharp intermittent noise should be provided with hearing protection.

Hearing Protection

There are three types of hearing protectors on the market today.

Ear plugs that can be inserted to block the ear canal. They may be preformed or foam ear plugs and are sold as disposable or reusable. Custom molded plugs are also available.

Semi-insert ear plugs are held over the ends of the ear canal by a thin rigid headband.

Ear plugs provide less protection than some ear muffs, and should not be used in areas having noise levels over 105 db. Since they are not as visible as muffs it may be more difficult for supervisors to ensure they are being worn. However, after wearing them on a few jobs, astute workers will soon understand the benefits of a worksite policy requiring hearing protection as they will feel less fatigued and irritable after a day of noise exposure. Naturally plugs must be inserted properly to provide protection.

To fit the ear plug the ear should be pulled outward and upward with the opposite hand to enlarge and straighten the ear canal. Clean your hands before inserting ear plugs and wash or replace them on a daily basis to avoid ear infections.

Ear muffs are made of sound-attenuating material formed into soft ear-cushions in a hard outer cup. A thick slightly flexible head band holds each cup in a tight seal over the ear. Quality ear muffs will provide greater protection than earplugs.

When purchasing ear muffs look for a dome deep enough to cover your ears. The deeper and heavier the dome, the greater the low-frequency attenuation. Although awkward to wear in some situations, they are generally easier to fit and last longer than plugs. They are, however more expensive and, in hot work areas an be less comfortable than simple plugs.

In areas where the noise level is high, ear plugs and earmuffs may be worn together.

Wear Them on the Job…Always

Hearing protection, whether plugs or muffs must be worn at all times to avoid hearing deterioration over the long term. Studies have shown that during an eight-hour shift if an individual removes hearing protection for 40 minutes, rather than receiving the equivalent of protection equal to 30 decibels, the protection equivalent drops to 10 decibels.

Senior management, Human Resources and line managers should work together to reduce the long-term impact of noise on employees' hearing. Management should contact the agency responsible for occupation health and safety within their province to ensure workplace standards are up to date and get educational literature to provide to employees.