Acoustic trauma

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Acoustic trauma
Specialty Audiology

Acoustic trauma is the sustainment of an injury to the eardrum as a result of a very loud noise. Its scope usually covers loud noises with a short duration, such as an explosion, gunshot or a burst of loud shouting. Quieter sounds that are concentrated in a narrow frequency may also cause damage to specific frequency receptors. [1] The range of severity can vary from pain to hearing loss. [2]

Contents

Acute acoustic trauma can be treated by combining hyperbaric oxygen therapy (HBO) with corticosteroids. Acute noise exposure causes inflammation and lower oxygen supply in the inner ear. Corticosteroids hinder the inflammatory reaction and HBO provides an adequate oxygen supply. This therapy has been shown to be effective when initiated within three days after acoustic trauma. Therefore, this condition is considered an ENT emergency. [3]

Signs and Symptoms

Hazardous noise causes injury to the hearing mechanisms in the inner ear. Acoustic trauma may result in sensorineural HL (SNHL) that is either temporary (temporary threshold shift, TTS) or permanent (permanent threshold shift, PTS). A TTS will resolve with time, while the time frame for hearing recovery is unique in every case, any SNHL that persists beyond eight weeks after injury is most likely permanent and should be considered PTS. [4]

Causes

Acoustic trauma is an injury to the inner ear that's often caused by exposure to a high-decibel noise. This injury can occur after exposure to a single, very loud noise or from exposure to noises at significant decibels over a longer period of time.[ citation needed ] Many cases have included a period of reduced hearing after exposure to loud sounds. Examples include after a concert or a visit to a discotheque or having worked with noisy equipment. This kind of hearing impairment is often temporary. After some recovery time, the acoustic trauma often will stop. [5]

Threshold of Hearing (Decibel, dB)

Pathophysiology

Acoustic trauma occurs when a continuous transient sounds transfers enough energy to a cochlea to result in necrosis of the outer hair cells (OHC), inner hair cells (IHC), and cause glutamate excitotoxicity of first-order afferent neurons of the spiral ganglion (cochlear synaptopathy). This can occur when an impact or impulse sound like an explosion occurs abruptly. When excessive, this force can lead to cellular metabolic overload, cell damage and cell death. [7] The force of that transient sound exceeds the elastic limit of the tissues. The organ of Corti can be sheared off the basilar membrane when the sound coming through the ear canal, middle ear and cochlea exceeds 132 dB. If the sound is more intense than 184 dB, the eardrum is ruptured. 184 dB and above usually comes from military sound exposures, such as with the explosion of an IED (improvised explosive device). When a person has a shock wave, not only is the eardrum ruptured, but also has ossicular discontinuities. The explosion or blast if powerful can cause traumatic brain injury. As a result, a person could have an auditory processing disability. Lung injures can develop as well as some injuries to the viscera. [8] Once exposure to damaging noise levels is discontinued, further significant progression of hearing loss stops. Individual susceptibility to noise-induced hearing loss varies greatly, but the reason that some people are more resistant to it while others are susceptible is not well understood. [7]

Diagnosis

The diagnosis is based on what environmental factors of that loud noise that was exposed. Audiometry will be used to detect signs of acoustic trauma. In this test, there are different sounds of varying loudness and of different tones that are exposed to more carefully assess what can be heard and what can't be heard. [5]

Treatment/Prevention

There are various treatment methods available depending on how severe the acoustic trauma is. Acoustic trauma cannot be reversed as of today. The goal of treatment is to protect the ear from further damage. [9] Below are possible preventive measures and treatment methods that could help in cases of acoustic trauma

Prognosis

Each episode of acoustic trauma results in permanent damage within the inner ear, even though the majority of patients, the symptoms will disappear and an audiogram will show normal hearing within a few hours to a few days. In some cases, the changes seen in the audiogram will only partially improve or remain permanent. One of the signs and symptoms of acoustic trauma is tinnitus and this may persist for a long time. In some cases, tinnitus may become a permanent condition. [10] There is no specific study done on Life Expectancy or statistical information for the prognosis of acoustic trauma. Overall, depending on how powerful the noise was and how and what degree of the severity, the prognosis is quite difficult to predict. [11]

Epidemiology

The prevalence depends on the environmental factors. Acoustic trauma is quite common during military service and during hunting activities where it's mainly associated with gun sports and particularly accidental shots. Of teenagers, 20-50 percent experience exposure to noise levels high enough to cause acute acoustic trauma. [10] Hearing loss due to noise is the second most common sensorineural hearing loss, after age-related hearing loss (presbycusis). Of more than 28 million Americans with some degree of hearing impairment, as many as 10 million have hearing loss caused by in part by excessive noise exposure in the workplace or during recreational activities. [12]

See also

Related Research Articles

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Hearing loss is a partial or total inability to hear. Hearing loss may be present at birth or acquired at any time afterwards. Hearing loss may occur in one or both ears. In children, hearing problems can affect the ability to acquire spoken language, and in adults it can create difficulties with social interaction and at work. Hearing loss can be temporary or permanent. Hearing loss related to age usually affects both ears and is due to cochlear hair cell loss. In some people, particularly older people, hearing loss can result in loneliness. Deaf people usually have little to no hearing.

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Tinnitus is a variety of sound that is heard when no corresponding external sound is present. Nearly everyone experiences faint "normal tinnitus" in a completely quiet room; but it is of concern only if it is bothersome, interferes with normal hearing, or is associated with other problems. The word tinnitus comes from the Latin tinnire, "to ring". In some people, it interferes with concentration, and can be associated with anxiety and depression.

<span class="mw-page-title-main">Ear</span> Organ of hearing and balance

An ear is the organ that enables hearing and body balance using the vestibular system. In mammals the ear is usually described as having three parts: the outer ear, the middle ear and the inner ear. The outer ear consists of the pinna and the ear canal. Since the outer ear is the only visible portion of the ear in most animals, the word "ear" often refers to the external part alone. The middle ear includes the tympanic cavity and the three ossicles. The inner ear sits in the bony labyrinth, and contains structures which are key to several senses: the semicircular canals, which enable balance and eye tracking when moving; the utricle and saccule, which enable balance when stationary; and the cochlea, which enables hearing. The ear is a self cleaning organ through its relationship with earwax and the ear canals. The ears of vertebrates are placed somewhat symmetrically on either side of the head, an arrangement that aids sound localization.

<span class="mw-page-title-main">Conductive hearing loss</span> Medical condition

Conductive hearing loss (CHL) occurs when there is a problem transferring sound waves anywhere along the pathway through the outer ear, tympanic membrane (eardrum), or middle ear (ossicles). If a conductive hearing loss occurs in conjunction with a sensorineural hearing loss, it is referred to as a mixed hearing loss. Depending upon the severity and nature of the conductive loss, this type of hearing impairment can often be treated with surgical intervention or pharmaceuticals to partially or, in some cases, fully restore hearing acuity to within normal range. However, cases of permanent or chronic conductive hearing loss may require other treatment modalities such as hearing aid devices to improve detection of sound and speech perception.

<span class="mw-page-title-main">Sensorineural hearing loss</span> Hearing loss caused by an inner ear or vestibulocochlear nerve defect

Sensorineural hearing loss (SNHL) is a type of hearing loss in which the root cause lies in the inner ear or sensory organ or the vestibulocochlear nerve. SNHL accounts for about 90% of reported hearing loss. SNHL is usually permanent and can be mild, moderate, severe, profound, or total. Various other descriptors can be used depending on the shape of the audiogram, such as high frequency, low frequency, U-shaped, notched, peaked, or flat.

Hyperacusis is the increased sensitivity to sound and a low tolerance for environmental noise. Definitions of hyperacusis can vary significantly; it can refer to normal noises being perceived as: loud, annoying, painful, fear-inducing, or a combination of those, and is often categorized into four subtypes: loudness, pain, annoyance, and fear.

Presbycusis, or age-related hearing loss, is the cumulative effect of aging on hearing. It is a progressive and irreversible bilateral symmetrical age-related sensorineural hearing loss resulting from degeneration of the cochlea or associated structures of the inner ear or auditory nerves. The hearing loss is most marked at higher frequencies. Hearing loss that accumulates with age but is caused by factors other than normal aging is not presbycusis, although differentiating the individual effects of distinct causes of hearing loss can be difficult.

<span class="mw-page-title-main">Audiogram</span> Graph showing audible frequencies

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<span class="mw-page-title-main">Perforated eardrum</span> Injury leading to a hole in the eardrum

A perforated eardrum is a hole in the eardrum. It can be caused by infection, trauma, overpressure, inappropriate ear clearing, and changes in middle ear pressure. An otoscope can be used to view the eardrum to diagnose a perforation. Perforations may heal naturally, or require surgery.

Listener fatigue is a phenomenon that occurs after prolonged exposure to an auditory stimulus. Symptoms include tiredness, discomfort, pain, and loss of sensitivity. Listener fatigue is not a clinically recognized state, but is a term used by many professionals. The cause for listener fatigue is still not yet fully understood it is thought to be an extension of the quantifiable psychological perception of sound. Common groups at risk of becoming victim to this phenomenon include avid listeners of music and others who listen or work with loud noise on a constant basis, such as musicians, construction workers and military personnel.

<span class="mw-page-title-main">Noise-induced hearing loss</span> Medical condition

Noise-induced hearing loss (NIHL) is a hearing impairment resulting from exposure to loud sound. People may have a loss of perception of a narrow range of frequencies or impaired perception of sound including sensitivity to sound or ringing in the ears. When exposure to hazards such as noise occur at work and is associated with hearing loss, it is referred to as occupational hearing loss.

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Acoustic shock is the set of symptoms a person may experience after hearing an unexpected, loud sound. The loud sound, called an acoustic incident, can be caused by feedback oscillation, fax tones, or signalling tones. Telemarketers and call centre employees are thought to be most at risk.

Diplacusis, also known as diplacusis binauralis, binauralis disharmonica or interaural pitch difference (IPD), is a hearing disorder whereby a single auditory stimulus is perceived as different pitches between ears. It is typically experienced as a secondary symptom of sensorineural hearing loss, although not all patients with sensorineural hearing loss experience diplacusis or tinnitus. The onset is usually spontaneous and can occur following an acoustic trauma, for example an explosive noise, or in the presence of an ear infection. Sufferers may experience the effect permanently, or it may resolve on its own. Diplacusis can be particularly disruptive to individuals working within fields requiring acute audition, such as musicians, sound engineers or performing artists.

Tinnitus maskers are a range of devices based on simple white noise machines used to add natural or artificial sound into a tinnitus sufferer's environment in order to mask or cover up the ringing. The noise is supplied by a sound generator, which may reside in or above the ear or be placed on a table or elsewhere in the environment. The noise is usually white noise or music, but in some cases, it may be patterned sound or specially tailored sound based on the characteristics of the person's tinnitus.

Auditory fatigue is defined as a temporary loss of hearing after exposure to sound. This results in a temporary shift of the auditory threshold known as a temporary threshold shift (TTS). The damage can become permanent if sufficient recovery time is not allowed before continued sound exposure. When the hearing loss is rooted from a traumatic occurrence, it may be classified as noise-induced hearing loss, or NIHL.

<span class="mw-page-title-main">Occupational hearing loss</span> Form of hearing loss

Occupational hearing loss (OHL) is hearing loss that occurs as a result of occupational hazards, such as excessive noise and ototoxic chemicals. Noise is a common workplace hazard, and recognized as the risk factor for noise-induced hearing loss and tinnitus but it is not the only risk factor that can result in a work-related hearing loss. Also, noise-induced hearing loss can result from exposures that are not restricted to the occupational setting.

Middle ear barotrauma (MEBT), also known to underwater divers as ear squeeze and reverse ear squeeze, is an injury caused by a difference in pressure between the external ear canal and the middle ear. It is common in underwater divers and usually occurs when the diver does not equalise sufficiently during descent or, less commonly, on ascent. Failure to equalise may be due to inexperience or eustachian tube dysfunction, which can have many possible causes. Unequalised ambient pressure increase during descent causes a pressure imbalance between the middle ear air space and the external auiditory canal over the eardrum, referred to by divers as ear squeeze, causing inward stretching, serous effusion and haemorrhage, and eventual rupture. During ascent internal over-pressure is normally passively released through the eustachian tube, but if this does not happen the volume expansion of middle ear gas will cause outward bulging, stretching and eventual rupture of the eardrum known to divers as reverse ear squeeze. This damage causes local pain and hearing loss. Tympanic rupture during a dive can allow water into the middle ear, which can cause severe vertigo from caloric stimulation. This may cause nausea and vomiting underwater, which has a high risk of aspiration of vomit or water, with possibly fatal consequences.

References

  1. ↑ Oberhaus, Daniel (5 April 2018). "A Former NASA Scientist Almost Lost His Hearing Because of a Toilet Lid". Motherboard. Vice Media . Retrieved 5 April 2018.
  2. ↑ "Slideshow: Top Causes of Severe Hearing Loss". webmd.com.
  3. 1 2 3 Bayoumy, AB; van der Veen, EL (2019). "Effect of hyperbaric oxygen therapy and corticosteroid therapy in military personnel with acute acoustic trauma". Journal of the Royal Army Medical Corps. 166 (4): jramc–2018–001117. doi:10.1136/jramc-2018-001117. PMID   30612101. S2CID   58655791.
  4. 1 2 Esquivel, Carlos (5 September 2018). "Aural Blast Injury/Acoustic Trauma and Hearing Loss". Military Medicine. 183 (suppl_2): 78–82. doi: 10.1093/milmed/usy167 . PMID   30189086. Archived from the original on 2020-11-17.
  5. 1 2 3 4 5 "Acoustic trauma - What is an acoustic trauma? | Learn more!". www.hear-it.org. Retrieved 2020-11-12.
  6. ↑ SpeakerMasters (2019-04-04). "Noise Level Chart: Decibel Levels of Common Sounds With Examples". BoomSpeaker.com. Retrieved 2020-11-12.
  7. 1 2 Rabinowitz, Peter (2000-05-01). "Noise-Induced Hearing Loss". American Family Physician. 61 (9): 2749–2756. ISSN   0002-838X. PMID   10821155.
  8. ↑ Fligor, Brian J. "Acoustic Trauma from Recreational Noise Exposures Brian J. Fligor". AudiologyOnline. Retrieved 2020-11-12.
  9. 1 2 "Acoustic trauma: MedlinePlus Medical Encyclopedia". medlineplus.gov. Retrieved 2020-11-12.
  10. 1 2 3 "Acute acoustic trauma | Evidence-Based Medicine Guidelines". evidence.unboundmedicine.com. Retrieved 2020-11-12.
  11. ↑ Harada, Hirofumi; Shiraishi, Kimio; Kato, Toshihiko (2001-04-01). "Prognosis of acute acoustic trauma: a retrospective study using multiple logistic regression analysis". Auris Nasus Larynx. 28 (2): 117–120. doi:10.1016/S0385-8146(00)00117-6. ISSN   0385-8146. PMID   11240317.
  12. ↑ Rabinowitz, Peter (2000-05-01). "Noise-Induced Hearing Loss". American Family Physician. 61 (9): 2749–2756. ISSN   0002-838X. PMID   10821155.
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