Need To Know: Noise & Hearing Protection


“Sound is what we hear. Noise is unwanted sound”“Sound is what we hear. Noise is unwanted sound” as defined by the OSH Answers, noise can be continuous, variable, intermittent or impulsive depending on how it changes over time.

As measured in decibels (dB) or A-weighted decibels (dBA), sound around us such as a normal conversation can produce about 65 dBA, hair dryer/ lawnmower about 90 dBA, concert/ sporting event/ ambulance siren about 120 dBA, and fireworks display/ jet engine at takeoff about 140dBA.

According to the ACGIH established exposure guidelines for occupational exposure to noise in their Threshold Limit Values (TLVs) (85 dBA PEL with a 3 dBA exchange rate), a noise level over 85 dBA each day increases the risk factor for hearing damage.

SOLUTION: How to reduce noise?

First, use a quieter process or equipment to avoid loud and unpleasant noise;

Second, keep yourself away from noisy machinery, or limit the time spent in noisy areas;

Third, use hearing protection device, for instance, earplugs and earmuffs.

In most settings and activities, hearing protectors might be the best and the most practical solution.

Generally, there are three types of noise cancellation – passive, active and adaptive, among which, passive noise cancellation (PNC) and active noise cancellation (ANC) are two of the common types. Then what are the differences between PNC and ANC?

Briefly, passive noise cancellation is a method of naturally muffling noises by sound-absorbing acoustic foam and thicker ear cups sealing around the ear. While active noise cancellation actively blocks out external noise by digital or analog circuitry compressing or cancelling any noise above a prescribed level.

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OPTION: What types of hearing protectors are available?

Pre-molded/ reusable earplugs, canal caps, and non-electrical earmuffs are available hearing protectors featuring passive noise cancellation, while most electronic earmuffs actively attenuate noise via noise-cancelling technology. Both types of hearing protectors provide a certain noise reduction rating (NRR) or signal-to-noise ratio (SNR) value of its effectiveness of noise reduction or attenuation.

Though PNC and ANC technologies have several distinctions, they have their own advantages and limitations. A proper combination for maximum cancellation may be a good choice. However, one thing must be clear; to combine earplugs and earmuffs does not mean to double the efficiency. In fact, the dual protection actually only provides an additional 5 dB of hearing protection.

ALWAYS wear hearing protectors correctly for optimal fit and protection.


  • It is important to maintain hearing protectors for long-lasting noise reduction, hygiene and comfort.
  • Do not immerse hearing protectors in water; only wipe the surface with damp cloth; and store in a case to prevent exposure to excessive heat or moisture when not in use.
  • Check earmuffs on a regular basis for possible defects, such as cracks, deformed shape or reduced tension, and use hygiene kits to maintain or replace if necessary.
  • The cushion should be changed every six months and the entire earmuff should be replaced every two years.