MISSISSAUGA, Ont.—Most safety managers know repeated exposure to loud noise can cause hearing loss in manufacturing plants. But they may not realize pitch or frequency can cause more problems than intensity of noise alone, according to one occupational health and safety specialist.
Speaking at the Partners in Prevention show in Toronto recently, Susan Ing, occupational health and safety specialist with Workplace Safety and Prevention Services in Mississauga, Ont., said most of her investigations reveal irritating high and low tones are the biggest causes for complaints.
While high and low pitches falling below the 85 decibel threshold—the eight-hour exposure level at which employers must take action in Ontario— won’t cause hearing loss, they can result in headaches, low productivity and ultimately, an unhappy workforce, she says.
Proper assessment of employee exposure to noise is essential to determine whether your workplace needs a hearing loss conservation plan.
“If you’ve got numbers that for some reason don’t explain the issue you’re having with your site, take a look at the pitch,” she adds.
If investigations reveal employee exposure exceeds the exposure limit for their jurisdiction, employers must put a formal plan in place to prevent noise-induced hearing loss.
The formal plan should include training employees on the proper use of ear protection, and posting warning signs.
Readings can be done in-house with a sound-level meter, a calibrator and a noise dosimeter. Dosimeters provide more accurate readings of noise exposure over a work shift, because they’re designed to be worn all day.
Ing warns against using mobile phone applications to measure noise levels because they can’t be calibrated. They’re suitable for initial screenings but they aren’t credible beyond that.
Once the problem has been determined, employers can take a variety of steps to prevent hearing damage among its staff.
Ing offered the following tips:
• Moving loud equipment. Doubling the distance between a worker and the source of noise can reduce sound intensity by up to six decibels.
• Minimize vibration of machinery by tightening parts or panels, covering them with noise dampening materials, and installing acoustic enclosures,
• Control the transmission of vibration—a common pitch problem—by installing dampeners.
• Minimize impact noise by tilting receptacle plates and covering it with a rubbery material.
• Aerodynamic noise can be mitigated by avoiding discontinuities in the air stream, using exhaust mufflers for air jets and by reducing velocity of the jet.
If initial noise levels are in the range 85 to 90 dB, it’s unlikely engineering controls will bring it down to 80 dB, so it’s essential to provide proper ear protection.
The challenge with ear protectors is ensuring proper use because they’re often uncomfortable, she said. As such, a reduction of 10 decibels is the best you can expect from any form of ear protection.
In the end, workers must take responsibility to protect their own hearing but it’s the employer’s duty to provide them with the necessary education and tools to do so.