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Noise-induced Hearing Loss

When Noise Hurts

Noise induced hearing loss (NIHL) is irreversible hearing damage resulting from exposure to high levels of noise. NIHL affects an estimated 10 to 15 million people in the USA, making excessive noise exposure the most common cause of hearing loss.

What causes NIHL? Exposure to traumatic noise will cause permanent damage to the sensitive hair cells of the inner ear and possibly the hearing nerve.

NIHL is related to both noise intensity and the duration of exposure. Louder sounds require shorter exposures before damage occurs. Why? Because a 10 dB increase in sound level causes a 10 fold increase in sound intensity.

This means that the sound of an MP3 player set at a volume of 115 dB is about 1000 times more intense than a vacuum cleaner sound volume of 85 dB, and a Rock concert can produce sounds (120 dB) that are 100 times more intense than a lawnmower (100 dB)!

NIHL is Permanent. It can be treated to some extent (depending on the damage), but it can’t be reversed!

See our Brochure on Noise-induced hearing loss, here

When Sound Hurts

NIHL

NIHL is related to both noise intensity and the duration of exposure. The relationship between sound levels and exposure limits is illustrated below.

The Table (below) shows how quickly sound tolerance limits decrease with small increases in sound intensity levels. Recall, this is because an increase of 10 dB corresponds to a 10 fold increase in sound intensity. Simply put, the louder the sound, the shorter the time before damage occurs..and the relationship isn’t linear! Here’s an important take-away: there are no treatments…not medicine, not surgery, not hearing aids…that can restore your natural hearing once it is damaged by noise.

The Table (below) shows the intensity range of everyday sounds. We prefer to use sound intensity ranges rather than absolute values because 1) every day sounds are better represented by a range and, 2) the difference between the low and high ends of a particular sound’s range can mean the difference between a relatively safe or a harmful experience. For example…a musical concert can range from 80 to 120 dB. You can listen to 80 dB all day without any risk of NIHL…but if the band is blasting out 120 dB you can safely listen for less than 9 minutes before NIHL becomes a serious consideration…depending on how close you are to the speakers.

The Bottom Line: The preceding tables indicate that long or repeated exposure to sounds at or above 85 dB can cause hearing loss, and progressively louder sounds allow shorter exposure limits before NIHL occurs. Noise and NIHL studies indicate that more than 15 minutes of unprotected exposure to 100 dB sounds, and regular exposure to sounds at 110 dB for more than one minute can lead to permanent hearing loss.

Although we can’t provide absolutes for decision making, the tables CAN provide important guidelines. If you plan to participate in activities that can produce sound intensity levels above 85 dB…be mindful of  your exposure time and proximity to the noise source. When in doubt…use ear protection. Remember…NIHL is nonrefundable!

Final Word…How Do We Avoid NIHL?

Noise-induced hearing loss is preventable. This article should increase your awareness of noise hazards and motivate you to protect your hearing. Our advice: be mindful of noises that can cause damage (those above 85 dB), your proximity to the noise, and the length of time you are exposed to the noise. Be especially wary if:

  • you have to raise your voice in normal conversation
  • the noise hurts your ears
  • you develop a continuous or temporary buzzing or ringing in your ears
  • normal hearing isn’t restored until several hours after you get away from a noise source.

Bottom Line: If you must remain in loud environment for any length of time wear ear plugs or other protective devices.

Dr. Li-Korotky AuD, PhD, MD, is President of Pacific Northwest Audiology (www.pnwaudiology.com) in Bend OR.

Age-Related Hearing Loss (ARHL)

Seeds of a Growing Problem

The population of the U.S. is getting older. According to the Administration on Aging, the aging ‘baby boom’ generation will produce a dramatic increase in the population through 2030. In 2009, people over 65 represented 12.9% of the population, but by 2030, they will represent 19.3%. The population over 65 is expected to double between 2008 and 2030 to a projected 72.1 million.

Why should we be concerned with an Aging Population? Because Hearing loss is the third most common chronic health condition among older adults! According to the National Institute on Deafness and Other Communication Disorders (NIDCD), 36 million Americans have impaired hearing, including 17% of our adult population. The occurrence of hearing loss increases with age. Approximately one third of Americans between 65 and 74 and nearly half of those over 75 have hearing and communication problems.

The Symptoms and Progress of ARHL

ARHL (also known as presbycusis) is a gradual and progressive hearing loss that affects most individuals as they age. Due to the slow progression, adults with ARHL may not realize that their hearing is diminishing …but if they do …they may accept it as normal aging. ARHL has a serious impact on the elderly because it diminishes their ability to communicate and reduces their functional independence. This limits their opportunities to participate effectively in their daily lives.

To those with ARHL, sounds often seem less clear and lower in volume. Muted murky sounds make it increasingly difficult to hear and understanding speech. Individuals with ARHL may experience several of the following:

  • The speech of others may seem mumbled or slurred.
  • It may become difficult to distinguish high-pitched sounds such as “s” and “th”.
  • Conversations become difficult to understand, especially when there is background noise.
  • A man’s voice may become easier to hear than the higher pitches of a woman’s voice.
  • Certain sounds may seem annoying or too loud.
  • Tinnitus (a ringing, roaring, or hissing sound in one or both ears) may develop.

Is ARHL the Same for Men and Women?

ARHL typically begins with high frequency hearing loss (degeneration of the hair cells lining the bottom of the Cochlea) and later affects the lower frequencies (apex of the Cochlea) as well. Paradoxically, several research studies indicate that while men develop high frequency hearing loss with age, women tend to have more problems discerning lower frequencies (250-1000Hz), possibly due to biologic factors such as hormones, or cardiovascular disease events (CVD) such as hypertension, coronary heart disease, stroke, and diabetes. While low-frequency hearing loss is related to CVD events in both genders, women tend to show this relationship more than men on audiograms. The figure (above) shows the gender reversal pattern, using average audiograms of 341 males and 346 females aged 50-89 years (Journal of the American Academy of Audiology (1993;4:42-49).

Although precise causes for this pattern require more research, the bottom line is that women with ARHL have more problems with low-pitched vowel sounds (o, a, ah, i, e), and men have more problems with high-pitched consonant sounds (d, t, sh, s, f, th). Since the softer high-pitched consonant sounds carry the meaning of speech, those (especially men) with pronounced high-frequency hearing loss often have problems understanding what is being said, especially in an environment with background noise.

About the Author

Dr. Li-Korotky is a nationally acclaimed research scientist and clinician, and the President of Pacific Northwest Audiology in Bend OR. The Doctor earned an MD with an emphasis in otology and otolaryngology, a PhD in audiology with a thesis on Age-Related Hearing Loss, and a Clinical Doctor of Audiology degree (AuD).