Quiet Ride

June 1, 2006
Schools and universities should pay attention to the noise their custodial equipment generates.

Several companies are marketing maintenance equipment to education institutions on a “quiet platform,” citing benefits such as a safer, more pleasant indoor environment and unobtrusive operations during day cleaning or operating hours. This is basically “sound advice” (no one likes noisy equipment), but some of the messages can be confusing and misleading.

Some myths center on sound safety, decibels and noise, and sound distractions:

  • Myth No. 1: Cleaning equipment is loud enough to cause hearing damage. Even with extended use, most cleaning equipment is not harmful to an operator's hearing — unless he or she cleans using a jackhammer. The Occupational Safety and Health Administration (OSHA) provides a 90-decibel short-term exposure or an 85-decibel average over eight hours as the threshold for sound levels that can cause hearing damage. The National Institute for Occupational Safety and Health (NIOSH) sets the bar at 85 decibels regardless of exposure time. If a school crew is using equipment as loud or louder than that (at the ear), the simplest solution is to have workers wear inexpensive foam earplugs. This will reduce sound levels by about 30 decibels.

    However, hearing protection is not necessary with most cleaning equipment. Newer commercial vacuum cleaners — the most audible of daily cleaning tools — range between 61 and 80 decibels.

  • Myth No. 2: Decibel numbers provided by manufacturers are a good way to compare equipment noise levels or loudness. Manufacturers have varying ways of measuring and reporting decibels, and no industry-wide consensus or regulatory standard has been established for how this should be done. Thus, it is impossible to do an apples-to-apples comparison among various companies' machines. Decibels may be measured in an anechoic chamber (a quiet chamber that produces no echo and thus yields a lower decibel reading); in other types of environments; or under different conditions, such as next to the motor, next to the ear or maybe even elsewhere in the room.

    ASTM has published a standard (ASTM F1334-02) for measuring vacuum cleaner decibel levels, but it is not used universally by all vacuum-cleaner makers.

  • Myth No. 3: Decibels tell the whole “noise” story. Decibels are a measure of air pressure created by sound waves and are an effective way to determine loudness. The pressure those waves make vibrate the eardrum, creating sound.

    However, decibels measure sound pressure; they do not measure frequency or tonal quality. Low, mid-range or high frequencies affect the perception and impact of sound. Thus, a sound with a lower decibel rating but a grating tone can be more irritating or harmful than a higher decibel sound with a more pleasant tone because of its frequency range.

    Also, the general question of how loud something is does not account for how far away a person is from the source of the noise, the type of room and its acoustics, the frequency of the sound, or whether the person has control over the sound level.

    So should maintenance personnel forget about decibel numbers altogether? No, but keep in mind that they do not tell the whole story.

  • Myth No. 4: The decibel level is the best way to determine if a sound is distracting. People hear and react to sounds — even the same ones — differently. Noise or distracting sounds are a subjective judgment or experience. Constant sounds tend to be less disturbing than variable and unexpected ones.

    For instance, the steady sound of a room air conditioner can be soothing to some people and annoying to others. The steady drip of a faucet may distract people trying to sleep, whereas if they are engaged in an activity, the sound might go unnoticed.

  • Myth No. 5: The sound of equipment never varies and cannot be controlled. Equipment sounds differ depending on operating conditions and the environment. Vacuums that are overfilled and clogging make a high-frequency sound as the motor speed increases. A propane scrubbing machine makes a different sound in use than when idling. An electric or propane burnisher may sound louder in a mid-sized retail store than in a cavernous shopping warehouse.

The ability to customize or adjust equipment sound output is an ideal solution, because it takes managers out of the dubious business of comparing unreliable and relative decibel numbers and into the practical realm of human hearing, perception and operational needs. Just adjust the sound to suit the operator and surroundings.

What's the answer? Check those decibels, but also trust your ears. Just as beauty is often in the eye of the beholder, noise sometimes can be determined best by the ear of the listener.

Find equipment that adjusts to the changing needs of circumstances, workers and customers for a cleaning approach that is both effective and non-disruptive.

Rathey is president of InstructionLink/JanTrain, Inc., Boise, Idaho.



Number of decibels allowed for safe, short-term exposure to noise.


Number of decibels allowed for safe noise over an eight-hour period.

Source: OSHA

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