You're mowing the lawn when your neighbour pops his head over the fence to say hi. He's an arm's length away, but you can barely hear him because of the motor. Sound familiar? Chances are, you haven't thought about what that noise means for your hearing.

"Most people don't give hearing protection at home much consideration," says Jodi Howick, chair of NAIT's Occupational Health and Safety program. "But the impacts of noise are the same, no matter where the exposure is experienced." Here, Howick gives a primer on protecting your hearing.

When to wear hearing protection

"From an occupational perspective, Alberta legislation requires hearing protection if noise levels are above 85 dBA over an eight-hour time period," says Howick. "But a good general test is if you have to raise your voice to speak to someone an arm's length away." If your ears ring or sounds seem muffled after exposure - even temporarily - you needed protection.

Earplugs or earmuffs?

"This is really a matter of choice as long as the protection fits and is worn properly," Howick says. "We want to reduce the noise level to between 70 and 85 dBA when we have hearing protection on."

Less than 70 is considered overprotection, which may prevent you from hearing safety alerts. To know you're reducing to an acceptable level, use what's called the Noise Reduction Rating (NRR), which is clearly indicated on earplugs and earmuffs available at the local hardware store.

Determining true NRR

Because the NRR is based on ideal lab conditions, follow these steps to determine the true dBA level with hearing protection for your situation.

1. Use these formulas to revise the NRR number

• Earmuffs: reduce the manufacturer's NRR by 25 per cent and then subtract seven.
• Formable earplugs: reduce the manufacturer's NRR by 50 per cent and then subtract seven.
• All other earplugs: reduce the manufacturer's NRR by 70 per cent and then subtract seven.

2. Determine the true dBA level with hearing protection by subtracting the revised NRR from the known dBA level for the activity.

HIGH def : d•B•A

Sound intensity is measured in decibels (dB). The A-scale accounts for how the ear perceives loudness. It is expressed as dBA.