Facts about Noise-Induced Hearing Loss

What is a noise-induced hearing loss?

Noise-induced hearing loss (NIHL) is the gradual loss of hearing due to exposure to harmful noise. When we are exposed to harmful noise over a period of time, the hair cells in our inner ear become damaged, resulting in a permanent hearing loss.

What types of noise causes NIHL?

NIHL can be caused by a one-time exposure to an intense “impulse” sound, such as an explosion, or by continuous exposure to loud sounds over an extended period of time. NIHL can be a result of recreational noise (concerts, motorcycles, woodworking), or it can be a result of occupational noise (factory noise, heavy equipment on a construction site).

How is noise measured and when is it too loud?

Sound is measured in units called decibels (dB). Alberta Occupational Health & Safety states that exposure to 85 dB(A) of noise, for more than eight hours per day can result in permanent hearing loss. Some examples of noise levels are as follows:

Sound Source:	Sound Pressure Level (dBA)
Normal conversation	50-60
Garbage disposal, blender, vacuum cleaner	80-85
Handheld drill, belt sander	87-100
Rock concerts, night clubs	100-120
Pneumatic jackhammers	110-120
Firecrackers and firearms	120-160

The louder the sound, the less time it takes to cause damage to your hearing. For every 3 dB increase in sound level, the amount of time you can safely be exposed to that noise is cut in half. The following table is taken from the Alberta Occupational Health and Safety Code 2009:

Table 16.1 Occupational exposure limits for noise

Exposure Level	Duration (dBA)
82	16 hours
83	12 hours and 41 minutes
84	10 hours and 41 minutes
85	8 hours
88	4 hours
91	2 hours
94	1 hour
97	30 minutes
100	15 minutes
103	8 minutes
106	4 minutes
109	2 minutes
112	56 seconds
115 and greater	0

Sounds of less than 75 decibels, even after long exposure, are unlikely to cause hearing loss.

How do I protect myself from NIHL?

The use of hearing protection when exposed to hazardous noise levels is important. Types of hearing protection include foam earplugs, ear muffs and custom hearing protection. Regular hearing tests are also important because they allow you to monitor any decreases in your hearing that may be caused by noise exposure. If hearing protection is unavailable, distancing yourself from the noise source and limiting your exposure time are also helpful. A general rule of thumb is, if you have to raise your voice to carry on a conversation from three feet away the noise level is likely at above 85 dB. If this is the case, protective measures should be taken.

What are the symptoms of NIHL?

When a person is exposed to loud noise over a long period of time, symptoms of noise induced hearing loss will increase gradually. Over time, the sounds a person hears may become distorted or muffled, and it may be difficult for the person to understand speech, especially when there are competing voices or background noise.

Can NIHL be prevented? 

Noise induced hearing loss is completely preventable. To protect your hearing:

• Know which noises can cause damage (those at or above 85 decibels).
• Wear earplugs or other hearing protective devices when exposed to hazardous noise.
• Be alert to hazardous noise in the environment.
• Protect the ears of children who are too young to protect their own.
• Make family, friends, and colleagues aware of the hazards of noise.

What should I do if I suspect I have NIHL?

If you suspect you have a hearing loss, the first thing to do is make an appointment for a hearing evaluation. Your hearing health care provider will determine the degree and extent of your hearing loss and what assistance is available to you. If you have an occupational hearing loss, you may also be eligible for additional assistance. If you would like more information about NIHL please contact us.

Raeanne Rowswell MSc, R.Aud, Aud(C)
Registered Audiologist