Hearing Loss and Aging, and Music

One in 10 Americans has enough hearing loss to cause serious communication problems. In people over the age of 60, this number increases to 30 percent and then to more than 50 percent. These numbers are pretty conservative since young people more often listen to very loud music in disco clubs, rock concerts, or through their earphones – which causes gradual loss of hearing over time, and with age such effects get only worse. We know that presbycusis (discussed below) causes hearing loss in high-frequency sounds. As a result, we must lose at least some ability to hear and tune notes correctly. The same piece of music you once knew and loved could be new music to your ears after certain age. How can we reduce such adverse effects? Loudspeakers are the main source of music in our homes and listening rooms, and careful choice of loudspeakers is critical. Different loudspeaker designs have different characteristics in terms of clarity and distortions they produce – both frequency and phase distortions. We have found that single-driver speaker designs excel in exactly these areas. Using ‘single source’ as a model – rather than multiple sources (loudspeaker drivers), and by eliminating crossover electronics results in dramatically improved clarity and reduced distortions. This isn’t going to solve the hearing loss problem but will certainly help us to better enjoy music, and for a longer time.

 

Early Warnings of hearing loss

  • Do people “mumble” ?
  • Do you frequently say “what?” or “Huh?”
  • Do you misunderstand names and numbers?
  • Do you like the TV/radio volume louder?
  • Do you have trouble hearing in noisy rooms?

Over 25 million Americans have some degree of hearing loss and, as the average age of the population increases, this number will rise.

– V. M. Bloedel Hearing Research Center Home

As we get older, our hearing begins to lose some of its sharpness and clarity. This process of age-related hearing loss is known as presbycusis. Hearing loss happens for many reasons. Some people lose their hearing slowly as they age. This condition is known as presbycusis (prez-buh-KYOO-sis). Doctors do not know why presbycusis happens, but it seems to run in families. Another reason for hearing loss may be exposure to too much loud noise. This condition is known as noise-induced hearing loss. Many construction workers, musicians, airport workers, tree cutters, and people in the armed forces have hearing problems because of too much exposure to loud noise. Sometimes loud noise can cause a ringing, hissing, or roaring sound in the ears, called tinnitus (tin-NY-tus).

About 40% of people over 65 have hearing loss, but estimates vary from 30% to 85% according to the criteria used. Only a fourth of people who need hearing aids wear them. About a fourth of those without aids are deprived because their doctors don’t screen or are not enthusiastic about hearing aids. But in three-fourths, this lack is due to poor public education and attitude. Eighteen million people have some hearing trouble in one or both ears, six million in both ears, and about 500,000 can’t even hear shouted speech. In a six year period, the population increased 6% and hearing loss skyrocketed 29%. Six out of ten with marked problems in hearing are over 65.

Ian Maclean Smith, M.D., Emeritus Professor

Department of Internal Medicine

University of Iowa Hospitals and Clinics

It used to be that people aged 65 and older were the most likely to need hearing aids, but now hearing loss is a baby boomer phenomenon — as President Bill Clinton recently demonstrated when he was fitted with hearing aids.

Presbycusis (prez-bee-KU-sis) is the most common hearing problem in older people. In fact, people over age 50 are likely to lose some hearing each year. Presbycusis is an ongoing loss of hearing linked to changes in the inner ear. People with this kind of hearing loss may have a hard time hearing what others are saying or may be unable to stand loud sounds.

Presbycusis is estimated to effect 30-35% of adults 65-75 years old and 40-45% of adults over 75 years old. Hearing loss associated with presbycusis is greater for high-frequency sounds. The hearing loss is gradual, so many adults do not even realize that their hearing is diminishing. Those who damage their ears through noise develop it sooner and people who live in noisy societies have more presbycusis than those who live in quiet environments.

Most cases of presbycusis include high-frequency sensitivity loss, which disrupts speech comprehension in proportion to the sensitivity loss. The condition worsens with age. Two major forms of presbycusis are sensory and strial. The sensory form is due to loss of outer hair cells in the inner ear and is associated with high-frequency loss. Most people with sensory presbycusis can hear speech but have difficulty in understanding it. That is, their auditory sensitivity is satisfactory but speech discrimination (which depends upon high frequency hearing ability) is reduced. Fortunately, modern hearing aids can correct the high-frequency loss and provide great benefit to the wearer.

The strial or metabolic form of presbycusis is less common and affects both the low and high frequencies. This form of hearing loss is due to pathology of the stria vascularis, which, through its metabolism, is the source of electrical energy driving the cochlea. Recently, it has been shown that strial presbycusis, which is more common in women than in men, is associated with cardiovascular disease. Although unproven as yet, it may be the case that measures to prevent cardiovascular disease, such as fitness and exercise, weight reduction, lowering of high cholesterol levels, smoking cessation, and diet modification, may delay its onset. This appears to be a logical but untested hypothesis.

References for Presbycusis

  • Destefano AL and others. Genomewide linkage analysis to presbycusis in the Framingham heart study. Arch Otolaryngol HNS. 2003 129:285-289

Noise is a common cause of hearing loss in the US. Twenty-five percent of the US work force is regularly exposed to potentially damaging noise (Suter and von Gierke, 1987). Because of occupational risk of noise induced hearing loss, there are government standards regulating allowable noise exposure. People working before the mid 1960’s may have been exposed to higher levels of noise where there were no laws in the USA mandating use of devices to protect hearing. An example of an audiogram showing noise induced hearing loss is shown below. There is a clear “notch” at 3000 hz, with better hearing at both lower and higher frequencies.

Noise can also cause a reversible hearing loss, called a temporary threshold shift. This typically occurs in individuals who are exposed to gunfire or firecrackers, and hear ringing in their ears after the event (tinnitus). Non-occupational noise is also regularly encountered during recreational activities and are a source of premature hearing reduction. Peak noise levels (in dB) are provided in the following table taken from Smith et al, 1999).

NOISE                                   LEVEL

Firecracker                          180 dB

Gunshot                              167 dB

Car Stereo                           154 dB

Children’s toys                  150 dB

Sporting events                127 dB

Rock Concert                     120 dB

Health Club                         120 dB

Motorboats                        115 dB

Video Arcade                     110 dB

Snowmobile                       99 dB

Movie                                   94 dB

New iMax and some other movie theaters are pushing volumes to dangerous levels of over 100 dB when people shouldn’t be exposed to such levels of noise more than for a few minutes. Recommended maximum allowable exposure times (by Nova Scotia Department of Labor) are :

16 hours for 80 dB sound

8 hours for 85 dB sound

4 hours for 90 dB sound

2 hours for 95 dB sound

1 hour for 100 dB sound

30 min for 105 dB sound

15 min for 110 dB sound

7.5 min for 115 dB sound

0 min for above 115 dB sound – there should be no exposure at this level!!!

With normal hearing, one can hear intensities from 0 dB to 140 dB. This corresponds to power ratio (defined as ratio of the highest audible intensity to the lowest audible intensity) equal to 100,000,000,000,000 (100 Trillion). This enormous number is because dB is a logarithmic (rather than a linear) unit of measure. For example, a 3 dB difference translates to 2X (two times), 6 dB difference to 8X, 9 dB difference to 16X etc. Dangerous Decibels is a site dedicated to noise-induced hearing loss issues.

References:

  • Clark, W. W. and B. A. Bohne (1999). “Effects of noise on hearing.” Jama 281(17): 1658-9.
  • Suter, A. H. and H. E. von Gierke (1987). “Noise and public policy.” Ear Hear 8(4): 188-91.

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