Occlusion Effect

Last updated: November 5, 2020

What Does Occlusion Effect Mean?

The occlusion effect occurs when a person hears a booming or hollowed echo-like sound during everyday activities like chewing or talking. These sounds usually escape through an open ear canal; when that canal is blocked, these sounds rebound, maximizing even low-frequency sounds.

Compared to a normal hearing capacity, the occlusion effect can boost low-frequency sound pressure in the ear canal by 20 decibels (dB) or more.

Safeopedia Explains Occlusion Effect

In terms of physics, a sound is created by vibration or disturbance that travels through any medium by transferring energy from one particle to another. While it is an important element in gauging distances of an object, conversing, or even listening to entertainment, anything beyond 85 dB is unbearable to human ears and can cause permanent damage.

The sound range goes up in an industrial setting, jeopardizing the hearing health of workers. If the noise levels are high and unobstructed, workers may also end up in fatal accidents since they might not be aware of any warning signals or instructions. Moreover, high exposure to noise for a prolonged period may also lead to hearing loss over time. Creating an occlusion effect to negate the external sound with the help of earmuffs and earplugs is the only solution to avoid this occupational hazard.

While there are positive effects of isolating the ears from the source of the noise, there are also some difficulties that should be considered. Below are some examples:

  • One’s own voice may sound different to an uncomfortable degree.
  • It may be difficult to converse with a another worker wearing earmuffs.
  • It endows a feeling of heaviness or fullness.
  • It adds to the pressure in the head.
  • Wearing earmuffs can be uncomfortable during warm summer months.
  • The user may feel entirely cut off from the environment he is working in.

Despite these challenges, it's important for industrial workers in an environment with a noise level greater than 105 dB to wear protective gear like earplugs, pre-molded earplugs, or custom-molded earplugs. As per the Hearing Conservation Amendment to the OSHA Noise Standards (1983), the noise level under the hearing protection should be 85 dB or less. NIOSH, on the other hand, has recommended that the noise level under the hearing protection should not be greater than 82 dB.

If the protection level is below the desired level of 15 dB, it is said to have too much attenuation and the wearer is said to be overprotected. This, in turn, results in complete isolation to the extent of not being able to hear any warning signals. It is difficult to determine the attenuation factor, which makes it challenging to design the ideal ear protection. There are a number of hearing aids available, but there is yet to be a design that workers are willing to wear daily.


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