Noise induced hearing loss
Encyclopedia
Noise-induced hearing loss (NIHL) is an increasingly prevalent disorder that results from exposure to high-intensity sound
, especially over a long period of time.
is transmitted into and through the auditory system
. An acoustic signal from an energy source, such as a radio, enters into the external auditory canal, and is funneled through to the tympanic membrane (eardrum). The tympanic membrane acts as an elastic diaphragm and drives the ossicular chain of the middle ear
system into motion. Then the middle ear ossicles transfer mechanical energy to the cochlea
by way of the stapes footplate hammering against the oval window of the cochlea. This hammering causes the fluid within the cochlea (perilymph
and endolymph
) to push against the stereocilia
of the hair cells, which then transmit a signal to the central auditory system within the brain. When the ear is exposed to excessive sound levels or loud sounds over time, the overstimulation of the hair cells leads to heavy production of reactive oxygen species, leading to oxidative cell death. In animal experiments, antioxidant vitamins have been found to reduce hearing loss even when administered the day after noise exposure. They were not able to fully prevent it.
NIHL is therefore the consequence of overstimulation of the hair cells and supporting structures. Structural damage to hair cells (primarily the outer hair cells) will result in hearing loss that can be characterized by an attenuation and distortion of incoming auditory stimuli.
There are two basic types of NIHL:
s, gunfire
, a large drum
hit loudly and firecrackers.
s, nightclub
s, excessive noise in the workplace, and personal media players
. The U.S. Department of Labor’s Occupational Safety and Health Administration
(OSHA) states that exposure to 85 dB
(A) of noise, known as an exposure action value
, for more than eight hours per day can result in permanent hearing loss (Occupational Health and Safety Administration [OSHA], 2002). Since decibels are based on a logarithmic scale
, every increase of 3 decibels SPL
results in a doubling of intensity
, meaning hearing loss can occur at a faster rate. Therefore, gradually developing NIHL occurs from the combination of sound intensity and duration of exposure.
Both NIHL caused by acoustic trauma and gradually developing NIHL can often be characterized by a specific pattern presented in audiological findings. NIHL is generally observed to affect a person’s hearing sensitivity in the higher frequencies, especially at 4000 Hz. "Noise-induced impairments are usually associated with a notch-shaped high-frequency sensorineural loss that is worst at 4000 Hz, although the notch often occurs at 3000 or 6000 Hz, as well" (Gelfand, 2001, p. 202). Doctoral students at the University of Iowa have termed this notch, specific to a noise-induced etiology, a "muna." The symptoms of NIHL are usually presented equally in both ears (Gelfand). Not all audiological results from patients with NIHL match the above description. Often a decline in hearing sensitivity will occur at frequencies other than at the typical 3000–6000 Hz range. Variations arise from differences in people’s ear canal resonance, the frequency of the harmful acoustic signal, and the length of exposure (Rösler, 1994). As harmful noise exposure continues, the commonly affected frequencies will broaden and worsen in severity (Gelfand). "NIHL usually occurs initially at high frequencies (3, 4, or 6 kHz), and then spreads to the low frequencies (0.5, 1, or 2 kHz)" (Chen, 2003, p. 55).
, with an additional 9 million exposed to solvents and metals that put them at risk for hearing loss. Occupational hearing loss is one of the most common occupational diseases. 49% of male miners have hearing loss by the age of 50. By the age of 60, this number goes up to 70%. The following is a list of occupations that are most susceptible to hearing loss:
to rock groups
, are exposed to high decibel
ranges. Although some rock musicians experience noise-induced hearing loss from their music, it is still debated as to whether classical musicians are exposed to enough high-intensity sound to cause hearing impairment
s.
Music-induced hearing loss is still a controversial topic for hearing researchers. While some studies have shown that the risk for hearing loss increases as music exposure increases, other studies found little to no correlation between the two. Experts at the 2006 "Noise-Induced Hearing Loss in Children at Work and Play" Conference agreed that further research into this field was still required before making a broad generalization about music-induced hearing loss. Given the extensive research suggesting that industrial noise
exposure can cause sensorineural hearing loss a link between hearing loss and music exposures of similar level and duration (to industrial noise) seems highly plausible. Determining which individuals or groups are at risk for such exposures may be a difficult task. Recent research suggests that despite concerns about the proliferation of personal music players, that in fact disco's, concerts and live music events may be more hazardous to youth's hearing.
(OSHA) describes standards for occupational noise exposure in articles 1910.95 and 1926.52 http://www.osha.gov. OSHA
states that an employer must implement hearing conservation programs for employees if the noise level of the workplace is equal to or above 85 dB(A) for an averaged eight-hour time period (Gelfand, 2001). OSHA also states that "exposure to impulsive or impact noise should not exceed 140 dB peak sound pressure level" (CFR 1910.95(b)(2)). The United States Department of Defense
(DoD) instruction 605512 has some differences from OSHA 1910.95 standard, for example, OSHA 1910.95 uses a 5 dB exchange rate and DoD instruction 605512 uses a 3 dB exchange rate.
Employees are required to wear hearing protection when it is identified that their eight-hour time weighted average (TWA) is above the exposure action value
of 90 dB. If subsequent monitoring shows that 85 dB is not surpassed for an eight-hour TWA, the employee is no longer required to wear hearing protection (OSHA 3074, 2002 (Revised)).
There is evidence that hearing loss can be minimized by taking megadoses of magnesium for a few days, starting as soon as possible after exposure to the loud noise. A magnesium-high diet also seems to be helpful as an NIHL-preventative if taken in advance of exposure to loud noises. Consuming sizable amounts of magnesium can be potentially harmful, so this treatment should be followed with caution.
There are currently no medical options for NIHL from noise-exposure which occurred more than a week previously. However, current research for the possible use of drug and genetic therapies look hopeful (National Institute on Deafness and Other Communication Disorders [NIDCD], 2006).
Sound
Sound is a mechanical wave that is an oscillation of pressure transmitted through a solid, liquid, or gas, composed of frequencies within the range of hearing and of a level sufficiently strong to be heard, or the sensation stimulated in organs of hearing by such vibrations.-Propagation of...
, especially over a long period of time.
Description
NIHL is a preventable hearing disorder that affects people of all ages and demographics.Mechanism
NIHL occurs when too much sound intensitySound intensity
Sound intensity or acoustic intensity is defined as the sound power Pac per unit area A. The usual context is the noise measurement of sound intensity in the air at a listener's location.-Acoustic intensity:...
is transmitted into and through the auditory system
Auditory system
The auditory system is the sensory system for the sense of hearing.- Outer ear :The folds of cartilage surrounding the ear canal are called the pinna...
. An acoustic signal from an energy source, such as a radio, enters into the external auditory canal, and is funneled through to the tympanic membrane (eardrum). The tympanic membrane acts as an elastic diaphragm and drives the ossicular chain of the middle ear
Middle ear
The middle ear is the portion of the ear internal to the eardrum, and external to the oval window of the cochlea. The mammalian middle ear contains three ossicles, which couple vibration of the eardrum into waves in the fluid and membranes of the inner ear. The hollow space of the middle ear has...
system into motion. Then the middle ear ossicles transfer mechanical energy to the cochlea
Cochlea
The cochlea is the auditory portion of the inner ear. It is a spiral-shaped cavity in the bony labyrinth, making 2.5 turns around its axis, the modiolus....
by way of the stapes footplate hammering against the oval window of the cochlea. This hammering causes the fluid within the cochlea (perilymph
Perilymph
Perilymph is an extracellular fluid located within the cochlea in two of its three compartments: the scala tympani and scala vestibuli. The ionic composition of perilymph is comparable to that of plasma and cerebrospinal fluid...
and endolymph
Endolymph
Endolymph is the fluid contained in the membranous labyrinth of the inner ear. It is also called Scarpa's fluid, after Antonio Scarpa.-Composition:...
) to push against the stereocilia
Stereocilia
In the inner ear, stereocilia are the mechanosensing organelles of hair cells, which respond to fluid motion in numerous types of animals for various functions, including hearing and balance. They are about 10–50 micrometers in length and share some similar features of microvilli...
of the hair cells, which then transmit a signal to the central auditory system within the brain. When the ear is exposed to excessive sound levels or loud sounds over time, the overstimulation of the hair cells leads to heavy production of reactive oxygen species, leading to oxidative cell death. In animal experiments, antioxidant vitamins have been found to reduce hearing loss even when administered the day after noise exposure. They were not able to fully prevent it.
NIHL is therefore the consequence of overstimulation of the hair cells and supporting structures. Structural damage to hair cells (primarily the outer hair cells) will result in hearing loss that can be characterized by an attenuation and distortion of incoming auditory stimuli.
Types
The ear can be exposed to short periods in excess of 120 dB without permanent harm — albeit with discomfort and possibly pain; but long term exposure to sound levels over 80 dB can cause permanent hearing loss.There are two basic types of NIHL:
- NIHL caused by acoustic trauma and
- gradually developing NIHL.
Acoustic trauma
NIHL caused by acoustic trauma refers to permanent cochlear damage from a one-time exposure to excessive sound pressure. This form of NIHL commonly results from exposure to high-intensity sounds such as explosionExplosion
An explosion is a rapid increase in volume and release of energy in an extreme manner, usually with the generation of high temperatures and the release of gases. An explosion creates a shock wave. If the shock wave is a supersonic detonation, then the source of the blast is called a "high explosive"...
s, gunfire
Gunfire
Gunfire can refer to:* Gunshot, the discharge of a firearm* Gunfire , a DC comic book superhero* Gunfire , a 1934 Western starring Rex Bell* Gunfire , a 1950 Western starring Don "Red" Barry...
, a large drum
Drum
The drum is a member of the percussion group of musical instruments, which is technically classified as the membranophones. Drums consist of at least one membrane, called a drumhead or drum skin, that is stretched over a shell and struck, either directly with the player's hands, or with a...
hit loudly and firecrackers.
Gradually developing NIHL
Gradually developing NIHL refers to permanent cochlear damage from repeated exposure to loud sounds over a period of time. Unlike NIHL from acoustic trauma, this form of NIHL does not occur from a single exposure to a high-intensity sound pressure level. Gradually developing NIHL can be caused by multiple exposures to any source of excessive volume, such as home and vehicle stereos, concertConcert
A concert is a live performance before an audience. The performance may be by a single musician, sometimes then called a recital, or by a musical ensemble, such as an orchestra, a choir, or a musical band...
s, nightclub
Nightclub
A nightclub is an entertainment venue which usually operates late into the night...
s, excessive noise in the workplace, and personal media players
Portable audio player
A portable audio player is a personal mobile device that allows the user to listen to recorded audio while mobile. Sometimes a distinction is made between a portable player, battery-powered and with one or more small loudspeakers, and a personal player, listened to with earphones.-History:Portable...
. The U.S. Department of Labor’s Occupational Safety and Health Administration
Occupational Safety and Health Administration
The United States Occupational Safety and Health Administration is an agency of the United States Department of Labor. It was created by Congress of the United States under the Occupational Safety and Health Act, signed by President Richard M. Nixon, on December 29, 1970...
(OSHA) states that exposure to 85 dB
Decibel
The decibel is a logarithmic unit that indicates the ratio of a physical quantity relative to a specified or implied reference level. A ratio in decibels is ten times the logarithm to base 10 of the ratio of two power quantities...
(A) of noise, known as an exposure action value
Exposure action value
An Exposure Action Value or Action Value is a limit set on occupational exposure to noise where beyond those values, employers must take steps to monitor the exposure levels. These levels are measured in decibels. The American Occupational Safety and Health Administration set the EAV to...
, for more than eight hours per day can result in permanent hearing loss (Occupational Health and Safety Administration [OSHA], 2002). Since decibels are based on a logarithmic scale
Logarithmic scale
A logarithmic scale is a scale of measurement using the logarithm of a physical quantity instead of the quantity itself.A simple example is a chart whose vertical axis increments are labeled 1, 10, 100, 1000, instead of 1, 2, 3, 4...
, every increase of 3 decibels SPL
Sound pressure
Sound pressure or acoustic pressure is the local pressure deviation from the ambient atmospheric pressure caused by a sound wave. Sound pressure can be measured using a microphone in air and a hydrophone in water...
results in a doubling of intensity
Sound intensity
Sound intensity or acoustic intensity is defined as the sound power Pac per unit area A. The usual context is the noise measurement of sound intensity in the air at a listener's location.-Acoustic intensity:...
, meaning hearing loss can occur at a faster rate. Therefore, gradually developing NIHL occurs from the combination of sound intensity and duration of exposure.
Both NIHL caused by acoustic trauma and gradually developing NIHL can often be characterized by a specific pattern presented in audiological findings. NIHL is generally observed to affect a person’s hearing sensitivity in the higher frequencies, especially at 4000 Hz. "Noise-induced impairments are usually associated with a notch-shaped high-frequency sensorineural loss that is worst at 4000 Hz, although the notch often occurs at 3000 or 6000 Hz, as well" (Gelfand, 2001, p. 202). Doctoral students at the University of Iowa have termed this notch, specific to a noise-induced etiology, a "muna." The symptoms of NIHL are usually presented equally in both ears (Gelfand). Not all audiological results from patients with NIHL match the above description. Often a decline in hearing sensitivity will occur at frequencies other than at the typical 3000–6000 Hz range. Variations arise from differences in people’s ear canal resonance, the frequency of the harmful acoustic signal, and the length of exposure (Rösler, 1994). As harmful noise exposure continues, the commonly affected frequencies will broaden and worsen in severity (Gelfand). "NIHL usually occurs initially at high frequencies (3, 4, or 6 kHz), and then spreads to the low frequencies (0.5, 1, or 2 kHz)" (Chen, 2003, p. 55).
Prevention
NIHL can easily be prevented through the use of some of the most simple, widely available and economical tools. This includes but is not limited to ear protection (i.e. earplugs and earmuffs), education, and hearing conservation programs. Earplugs and earmuffs can provide the wearer with at least 5 to 10 dB SPL of attenuation (Gelfand, 2001). According to a survey by Lass, Woodford, C. Lundeen, D. Lundeen and Everly-Myers (1987), which examined high school students’ attitudes and knowledge concerning hearing safety, 66% of the subjects reported a positive response to wearing hearing protection devices if educated about NIHL. Unfortunately, more often than not, individuals will avoid the use of ear protection due to embarrassment, lack of comfort, and reduced sound quality.Hearing loss in the workplace
About 30 million workers are exposed to hazardous noiseNoise
In common use, the word noise means any unwanted sound. In both analog and digital electronics, noise is random unwanted perturbation to a wanted signal; it is called noise as a generalisation of the acoustic noise heard when listening to a weak radio transmission with significant electrical noise...
, with an additional 9 million exposed to solvents and metals that put them at risk for hearing loss. Occupational hearing loss is one of the most common occupational diseases. 49% of male miners have hearing loss by the age of 50. By the age of 60, this number goes up to 70%. The following is a list of occupations that are most susceptible to hearing loss:
- AgricultureAgricultureAgriculture is the cultivation of animals, plants, fungi and other life forms for food, fiber, and other products used to sustain life. Agriculture was the key implement in the rise of sedentary human civilization, whereby farming of domesticated species created food surpluses that nurtured the...
- MiningMiningMining is the extraction of valuable minerals or other geological materials from the earth, from an ore body, vein or seam. The term also includes the removal of soil. Materials recovered by mining include base metals, precious metals, iron, uranium, coal, diamonds, limestone, oil shale, rock...
- ConstructionConstructionIn the fields of architecture and civil engineering, construction is a process that consists of the building or assembling of infrastructure. Far from being a single activity, large scale construction is a feat of human multitasking...
- ManufacturingManufacturingManufacturing is the use of machines, tools and labor to produce goods for use or sale. The term may refer to a range of human activity, from handicraft to high tech, but is most commonly applied to industrial production, in which raw materials are transformed into finished goods on a large scale...
- Utilities
- Transportation
- MilitaryMilitaryA military is an organization authorized by its greater society to use lethal force, usually including use of weapons, in defending its country by combating actual or perceived threats. The military may have additional functions of use to its greater society, such as advancing a political agenda e.g...
- MusicianMusicianA musician is an artist who plays a musical instrument. It may or may not be the person's profession. Musicians can be classified by their roles in performing music and writing music.Also....* A person who makes music a profession....
s - Orchestra conductors
Hearing loss for musicians
Musicians, from classical orchestrasOrchestra
An orchestra is a sizable instrumental ensemble that contains sections of string, brass, woodwind, and percussion instruments. The term orchestra derives from the Greek ορχήστρα, the name for the area in front of an ancient Greek stage reserved for the Greek chorus...
to rock groups
Rock Band
Rock Band is a music video game developed by Harmonix Music Systems, published by MTV Games and Electronic Arts. It is the first title in the Rock Band series. The PlayStation 3 and Xbox 360 versions were released in the United States on November 20, 2007, while the PlayStation 2 version was...
, are exposed to high decibel
Decibel
The decibel is a logarithmic unit that indicates the ratio of a physical quantity relative to a specified or implied reference level. A ratio in decibels is ten times the logarithm to base 10 of the ratio of two power quantities...
ranges. Although some rock musicians experience noise-induced hearing loss from their music, it is still debated as to whether classical musicians are exposed to enough high-intensity sound to cause hearing impairment
Hearing impairment
-Definition:Deafness is the inability for the ear to interpret certain or all frequencies of sound.-Environmental Situations:Deafness can be caused by environmental situations such as noise, trauma, or other ear defections...
s.
Music-induced hearing loss is still a controversial topic for hearing researchers. While some studies have shown that the risk for hearing loss increases as music exposure increases, other studies found little to no correlation between the two. Experts at the 2006 "Noise-Induced Hearing Loss in Children at Work and Play" Conference agreed that further research into this field was still required before making a broad generalization about music-induced hearing loss. Given the extensive research suggesting that industrial noise
Industrial noise
Industrial noise is usually considered mainly from the point of view of environmental health and safety, rather than nuisance, as sustained exposure can cause permanent hearing damage. Traditionally, occupational noise has been a hazard linked to heavy industries such as ship-building and...
exposure can cause sensorineural hearing loss a link between hearing loss and music exposures of similar level and duration (to industrial noise) seems highly plausible. Determining which individuals or groups are at risk for such exposures may be a difficult task. Recent research suggests that despite concerns about the proliferation of personal music players, that in fact disco's, concerts and live music events may be more hazardous to youth's hearing.
Workplace standards
The Occupational Safety and Health AdministrationOccupational Safety and Health Administration
The United States Occupational Safety and Health Administration is an agency of the United States Department of Labor. It was created by Congress of the United States under the Occupational Safety and Health Act, signed by President Richard M. Nixon, on December 29, 1970...
(OSHA) describes standards for occupational noise exposure in articles 1910.95 and 1926.52 http://www.osha.gov. OSHA
Occupational Safety and Health Administration
The United States Occupational Safety and Health Administration is an agency of the United States Department of Labor. It was created by Congress of the United States under the Occupational Safety and Health Act, signed by President Richard M. Nixon, on December 29, 1970...
states that an employer must implement hearing conservation programs for employees if the noise level of the workplace is equal to or above 85 dB(A) for an averaged eight-hour time period (Gelfand, 2001). OSHA also states that "exposure to impulsive or impact noise should not exceed 140 dB peak sound pressure level" (CFR 1910.95(b)(2)). The United States Department of Defense
United States Department of Defense
The United States Department of Defense is the U.S...
(DoD) instruction 605512 has some differences from OSHA 1910.95 standard, for example, OSHA 1910.95 uses a 5 dB exchange rate and DoD instruction 605512 uses a 3 dB exchange rate.
Employees are required to wear hearing protection when it is identified that their eight-hour time weighted average (TWA) is above the exposure action value
Exposure action value
An Exposure Action Value or Action Value is a limit set on occupational exposure to noise where beyond those values, employers must take steps to monitor the exposure levels. These levels are measured in decibels. The American Occupational Safety and Health Administration set the EAV to...
of 90 dB. If subsequent monitoring shows that 85 dB is not surpassed for an eight-hour TWA, the employee is no longer required to wear hearing protection (OSHA 3074, 2002 (Revised)).
Mitigation
For people living with NIHL, there are several management options that can improve the ability to hear and effectively communicate. Management programs for people with NIHL include counseling and the use of hearing aids and FM systems. With proper amplification and counseling, the prognosis is excellent for people with NIHL. The prognosis has improved with the recent advancements in digital hearing aid technology, such as directional microphones, open-fit hearing aids, and more advanced algorithms. Annual audiological evaluations are recommended to monitor any changes in a patient’s hearing and to modify hearing-aid prescriptions.There is evidence that hearing loss can be minimized by taking megadoses of magnesium for a few days, starting as soon as possible after exposure to the loud noise. A magnesium-high diet also seems to be helpful as an NIHL-preventative if taken in advance of exposure to loud noises. Consuming sizable amounts of magnesium can be potentially harmful, so this treatment should be followed with caution.
There are currently no medical options for NIHL from noise-exposure which occurred more than a week previously. However, current research for the possible use of drug and genetic therapies look hopeful (National Institute on Deafness and Other Communication Disorders [NIDCD], 2006).
See also
- Don't Lose The MusicDon't Lose The MusicDon’t Lose the Music is a national campaign launched by RNID, the charity representing the 9 million deaf and hard of hearing people in the UK.- Objectives :...
- H.E.A.R.H.E.A.R.H.E.A.R. is a non-profit organization dedicated to preventing hearing loss, mainly from loud rock music. The acronym stands for Hearing Education and Awareness for Rockers. It was founded in 1988 by rock musician Kathy Peck and physician Flash Gordon, M.D. after Kathy suffered tinnitus and...
- List of occupational health and safety awards
- NIOSH Power Tools DatabaseNIOSH Power Tools DatabaseThe NIOSH Power Tools Database contains sound power levels, sound pressure levels, and vibrations data for a variety of common power tools that have been tested by researchers. Data are collected for both the unloaded and loaded use of power tools...
- Safe-In-Sound Award
- TinnitusTinnitusTinnitus |ringing]]") is the perception of sound within the human ear in the absence of corresponding external sound.Tinnitus is not a disease, but a symptom that can result from a wide range of underlying causes: abnormally loud sounds in the ear canal for even the briefest period , ear...
- Youth hearing conservation programs
Further reading
- Chen, & Tsai. (2003). Hearing Loss among Workers at an Oil Refinery in Taiwan. Archives of environmental health, 58(1), 55-58.
- Fausti, S., Wilmington, D., Helt, P., Helt, W., & Konrad-Martin, D. (2005). Hearing Health and Care: The Need for Improved Hearing Loss Prevention and Hearing Conservation Practices. Journal of Rehabilitation Research & Development, 42(4), 45-62.
- Gelfand, S. (2001). Auditory System and Related Disorders. Essentials of Audiology: Second Edition (p. 202). New York: Thieme.
- Lass N.J., Woodford C.M., Lundeen C., Lundeen D.J., & Everly-Myers D. (1987) A Survey of High School Student’s Knowledge and Awareness of Hearing, Hearing Loss, and Hearing Health. The Hearing Journal, June 15–19.
- National Institute for Occupational Safety and Health. (2000). Work-Related Hearing Loss (Brochure). Washington, DC: National Institute for Occupational Safety and Health.
- National Institute on Deafness and Other Communication Disorders. (2006). Noise-Induced Hearing Loss. Retrieved March 3, 2007.
- Occupational Safety & Health Administration. (2002). Hearing Conservation. Retrieved March 3, 2007, from http://www.osha.gov/Publications/OSHA3074/osha3074.html
- Rösler, G. (1994). Progression of Hearing Loss Caused by Occupational Noise. Scandinavian Audiology 23, 13-37.
External links
- Noise-Induced Hearing Loss from the National Institutes of Health
- How to Prevent Noise-Induced Hearing Loss from the American Academy of Family PhysiciansAmerican Academy of Family PhysiciansThe American Academy of Family Physicians was founded in 1947 to promote the science and art of family medicine. It is one of the largest medical organizations in the United States, with over 100,000 members...
. - Dangerous Decibels Includes general information and a "virtual exhibit" as well as resources for teachers.
- NIOSH Noise and Hearing Loss Prevention Topic Page
- NIOSH Power Tools Sound Pressure and Vibrations Database
- New York City construction noise control products and vendor guidance sheet