HEARING LOSS IN MUSICIANS By Miriam C. Daum, P.T., M.P.H. Noise is defined as "unwanted sound". Although music is not generally thought of as an unwanted sound, in severe circumstances, prolonged exposure to loud music can result in hearing loss. During the last several years, both musicians and hearing specialists are becoming increasingly aware that both rock and classical music have the potential to produce noise-induced hearing loss. A 1981 study at Sweden's Concert Hall and Lyric Theatre in Gothenberg revealed that 59 out of 139 orchestra musicians (42%) had hearing losses greater than that expected for their ages. Other studies have found similiar results. Auditory acuity and sensitivity are especially important to the musician and even a subtle deficit may detract from the perfection of a performance. In extreme cases, severe hearing loss could mean an end to a musician's career. Exposure to excessive sound levels can cause damage in two ways: mechanical trauma and sensorineural hearing loss. Mechanical traumas, such as eardrum rupture or dislodgement of the middle ear bones, are the result of instantaneous noise, such as gunfire or explosions. Sensorineural hearing loss, caused by repeated exposure to excessive noise levels, is of most concern to musicians. In addition to the auditory effects, noise can cause physiological and/or psychological problems as well. The physiological effects may include a wide variety of symptoms including increased heart rate, blood pressure, breathing rate, muscle contractions and perspiration. Psychological complaints may include nervousness, tension, anger and irritability. This data sheet will discuss the causes of hearing loss, the effects of excessive exposure to potentially hazardous sound intensities, applicable federal regulations, and recommendations for prevention of auditory damage. EFFECTS OF NOISE How We Hear Sound is initiated by a mechanical force, such as the hammer inside a piano striking a string and a column of air being blown through a trumpet. Vibrations are produced as the density of air molecules are compressed and released in a periodic wave-like motion (similiar to the ripples in water created by a pebble that has hit it). When these vibrations enter the outer ear and strike the eardrum, it will vibrate. Sound waves are then transmitted mechanically through the ossicles (three small bones in the middle ear), to the inner ear, where, as hydraulic waves, they stimulate sensory hair cells in the cochlea. It is the movement of these cochleal cells that generates nerve impulses traveling via the auditory nerve to the brain, where they are interpreted as differentiated, meaningful sounds. The cochlear membrane receives a vast range of sound frequencies. Higher frequency receptors are located at the base of the cochlea, while the lower frequencies primarily are directed at the apex of the membrane. Most of the damaging effects of long-term noise occur in the sensory cells of the cochlea, explaining the term sensorineural hearing loss. Characteristics of Sound The two major characteristics of sound are intensity and frequency. Intensity, generally perceived as loudness, is measured in decibels (dB), on a logarithmic scale. This means that 90 dB is 10 times more intense than 80 db; 100 dB is 100 times more intense than 80 dB. The sound intensity doubles for every increase of 3 dB. Small increases in decibel level can involve a large increase in actual sound intensity. Sound Pressure Levels Whisper 20 dB Conversation 60 dB Vacuum cleaner 80 dB Orchestral music 83-92 dB Subway 80-110 dB Rock music band 105-111 dB Discotheque 120 dB Jet takeoff (300 feet distance) 140 dB Frequency, generally perceived as pitch, is measured in cycles per second or Hertz (Hz). The normal human ear can detect frequencies in the range of 16 Hz to 20,000 Hz. The normal speech range is 250-3000 Hz. How Hearing Loss Occurs The initial effect of high intensity sounds is sensory cell fatigue, which produces a temporary hearing deficit. This is termed a noise-induced temporary threshold shift. For example, a 25 dB temporary threshold shift means that a sound has to be 25 dB louder than before the exposure in order to be heard. The greatest amount of hearing loss occurs during the first two hours of exposure to excessive sound, after which it levels off. Recovery from a temporary threshold shift occurs gradually over the 14 hour period following noise exposure. The rapidity and degree of recovery depends upon the magnitude of the initial hearing loss, recovery time (i.e. amount of time away from noise) and individual susceptibility. If excessive noise exposure is repeated, usually over a period of years, the temporary threshold shift becomes irreversible. This is then termed a permanent noise induced threshold shift, or noise-induced hearing loss. Initially, noise-induced hearing loss occurs at 4000 Hz. With continued exposure, hearing loss will spread to both higher and lower frequencies. At the same time, the hearing sensitivity continues to decrease, and the minimal threshold for hearing a sound becomes higher. The actual degree of hearing impairment reflects an individual's total accumulation of noise exposure. This means that a musician's job-related hearing loss will be exacerbated by routine noise, such as that produced by subways, aircraft, and motorized equipment. Factors affecting hearing loss include the degree and type of noise (intensity and frequency), how frequently the individual is exposed, and the durations and type of noise (continuous, impact or impulse). Another major factor is individual susceptibility. Since no two individuals are physiologically identical, the same noise exposure may have markedly different affects on the individuals exposed. On the average, males appear to be more susceptible to hearing loss than females. Symptoms of Noise-Induced Hearing Loss One of the major problems with noise-induced hearing loss is that early warning signs, such as slight temporary hearing deficits after noise exposure, are seldom investigated. (For instance, tinnitus, described as ringing, buzzing, or hissing sounds in the ear, may be a symptom of excessive noise exposure, or it could be associated with numerous other medical conditions.) The destructive changes signaled by these symptoms occur slowly and progressively over many years and significant hearing loss becomes evident only after considerable permanent damage has occurred. "I hear fine, but everyone is mumbling" is a common response for someone experiencing noise-induced hearing loss. One of the first manifestations of loss is an inability to hear sounds with clarity. Because the person experiencing this may still have a normal perception of loudness, the change may not be recognized as hearing loss. An affected individual will typically have difficulty conversing in a crowded room, because of the presence of background noise. Some consonants such as s and t will appear particularly unclear. Another indication of hearing loss might be difficulty with understanding the speech of women and children as well as other high frequency sounds. Among engineers, producers and conductors, this condition is known as "tweeter burn", and is the result of exposure to loud volumes from both tweeter and bass woofer speakers. Hearing loss begins in the treble range, and problems develop when working with female voices. Later signs include a decreased ability to understand telephone conversations because visual input is eliminated and sensitivity is lost in the range that the telephone transmits. Presbycusis, or age-related hearing loss, occurs in the higher frequency ranges as well, although it usually appears as a sloping loss of sensitivity beginning at the highest frequencies and moving progressively into the lower ones. This is in contrast to the initial hearing loss at 4000 Hz found in noise-induced hearing loss. Damage incurred by excessive sound exposure, added to the gradual loss brought on by presbycusis, may result in an even greater total hearing deficit. PREVENTION OF HEARING LOSS Audiometric Testing Audiometric testing is the major component of a total hearing evaluation for suspected noise induced hearing loss. The person being tested listens for a series of tones (with different frequencies and intensities) through headphones. The individuals threshold of detection is graphically recorded on an audiogram. The threshold shifts (the shift in decibel level at which a particular sound frequency can be detected) are plotted for the sounds in 250-6000 Hz range. Noise-induced hearing loss first appears at 4000 Hz and then gets worse and broadens to include other frequencies with increasing years of exposure. Normally a threshold shift has to be greater than 20 dB to be considered significant. An initial audiogram should be performed as a baseline for comparison with future evaluations. In this way, any changes in an individual's hearing can be accurately assessed. If necessary, extension of hearing loss can be documented for potential Workers Compensation claims. Individuals undergoing audiometric testing are advised to remain free of noise exposure (including rehearsal, performance, and noisy machinery) for at least 14 hours prior to testing, as even a brief exposure may produce a temporary threshold shift and interfere with an accurate evaluation. If necessary, ear plugs can be worn for subway travel or other unavoidable noise exposures. Noise Monitoring Instruments Sound can be measured using three basic types of instruments: sound level meters, personal dosimeters and impulse meters. Portable sound level meters consist of a microphone, an electronic amplifier and a meter that indicates the decibel level. Octave band analyzers are sound level meters that measure the sound levels in specified frequency bands, in order to determine the frequency distribution of the sound. Personal sound monitors, also known as audio dosimeters, are measuring units worn by an individual for a specified time period. The total sound exposure is recorded and averaged, yielding the time-weighted average (TWA) used for OSHA compliance. Impulse or impact meters are utilized to measure high intensity, instantaneous noise lasting a fraction of a second (e.g. gunfire, hammer blows or drum beats). Although these various monitoring instruments are not very complex to use, their correct calibration and optimal placement is critical for an accurate assessment of noise exposure. Engineering Controls Noise controls can be focused to the source of the noise, along its path, or at your ear. When possible, control at either the source or along the path of noise is the method of choice. In industrial settings, this includes designing quieter machinery and enclosing or insulating noisy machinery. For musical performances, however, muting the instrument is usually not desirable or feasible. The primary focus must therefore be on control along the path of sound. In a symphony orchestra, a major source of high intensity sound is created by the brass and tympani sections. Therefore, effort should go into deflecting and decreasing the noise from these instruments. Methods for controlling this noise include erecting plexiglass shields in front of these sections to provide a partial barrier to excessive sound, or building risers for the rear section of the orchestra. Sound baffles on individual musicians' chairs may also deflect high intensity sounds in the surrounding areas. These control measures as well as others are being utilized by some orchestras. The effectiveness of these and other measures have not yet been accurately studied. Personal Protective Equipment Personal protective equipment (ear plugs and ear muffs) can also protect the musician. Standard earplugs are generally inexpensive and are available in rubber, plastic, wax, urethane, foam and impregnated cotton. (Plain cotton is not effective). Although plugs can be molded for individual users, "off the shelf" varieties made of resilient material are usually effective in conforming to individual ear shapes. Earmuffs are larger and more cumbersome than plugs but more effective. They are constructed of materials containing plastic or rubber foam and when well fit, provide a better acoustic seal than ear plugs. Earmuffs could also be equipped with speakers like those used for recording sessions. The Noise Reduction Ratio (NRR) is used to determine the effectiveness of ear protective devices. On the average, sound intensity is decreased by 15-30 dB when the subject is wearing correctly fitting plugs or muffs. APPLICABLE LAWS AND REGULATIONS OSHA Regulations The Occupational Safety and Health Administration (OSHA) regulates noise levels in the workplace. Under OSHA's mandatory occupational noise standard, exposure levels may not exceed an 8 hour Time Weighted Average (TWA) of 90 dB. Permissible decibel limits are adjusted for varying exposure durations (e.g. 4 hours - 95 dB, 2 hours - 100 dB etc.). The ceiling level is 115 dB, meaning that at no time may this level be exceeded. Impact or impulse noise may not exceed 140 dB at any time. Controversy exists about the 90 dB standard as it has been established that 20% of the general population could develop significant hearing loss at this level. Therefore, many experts believe that the standard should be lowered to 85 dB. If an 8 hour TWA noise exposure (or its equivalent) is measured at or greater than 85 dB, known as the "action level", employers must administer a hearing conservation program. This is mandatory under OSHA's 1983 hearing conservation amendment. This program is outlined below. OSHA Hearing Conservation Program 1. Periodic sound monitoring must be carried out with the use of appropriate instruments that are adequately checked and calibrated. Employees have a right to observe monitoring procedures and to be notified of monitoring results. 2. Baseline and annual audiometric testing must be provided, free of charge, to all employees exposed to a TWA of 85 dB or above. Testing must be conducted by a properly licensed or certified practitioner. Individuals tested must be notified, in writing, of any significant threshold shift, and referred for further audiological evaluation as necessary. 3. Suitable hearing protection (earplugs and earmuffs) must be made available, free of charge, to all employees exposed to noise levels of 85 dB or above. Instruction must be provided on the correct use and care of these devices. 4. A training program must be provided to all employees exposed to the noise action level. This program must include information on auditory effects of noise, hearing protection and audiometric testing. 5. Employers must maintain accurate records of employee noise exposure measurements, for a two year time period. Audiograms must be retained for the duration of an individual's employment at that workplace. Employees have the right of access to these records. Although these regulations were developed for industrial noise exposure, many of these provisions are also appropriate for musicians. Workers' Compensation In order to qualify for Workers' Compensation for noise- induced hearing loss, hearing impairment must be determined. Results are drawn from pure tone audiometric testing, conducted at frequencies of 500, 1000, 2000 and 3000 Hz (representing the primary speech frequency range). The auditory thresholds for the frequencies in each ear are then averaged. An average threshold shift must exceed 25 dB in order to be compensable. Frequencies above 3000 Hz are not included in Workers' Compensation audiometric testing; therefore, deficits in the ranges of 4000-8000 are not considered as compensable hearing loss. The rationale for this is that there is no interference with normal speech comprehension. This is unfortunate, as musicians experiencing high frequency range losses could be impacted in their performance, but can not be compensated. CONCLUSION Most of our accumulated data and research findings on noise-induced hearing loss have been obtained in the industrial setting (factories, construction sites, production plants, airfields, etc.) and control measures have been designed for those environments. Although initial studies of musicians indicated that high sound levels in musical performance can cause hearing loss, there are still many unanswered questions about the magnitude of the problem and potential solutions. As research progresses, new information continues to emerge, providing possibilities for preventative measures and techniques, thus allowing musicians to maintain their auditory "instruments" in the finest condition for the ultimate benefit of both performer and audience. REFERENCES Axelsson A and Lindgren F: Hearing in Classical Musicians. Acta Otolaryngol Suppl 1981; 377: 3-74. Jansson E et al: Sound Levels Recorded Within the Symphony Orchestra and Risk Criteria For Hearing Loss. Scand Audiol 1983; 12(3): 215-21. Karlsson K et al: The Hearing of Symphony Orchestra Musicians. Scand Audiol 1983; 12(4): 257-64. Kryter Karl D: The Effects of Noise on Man, Second Edition. Academic Press, New York, New York (1985). Lindgren F et al: Temporary Threshold Shift After Exposure To Noise and Music of Equal Energy. Ear Hear 1983; 4(4): 97-201. Lipscomb David M: Noise and Audiology. Baltimore University Park Press, Baltimore, Maryland (1978). Occupational Safety and Health Administration: Occupational Noise Exposure; Hearing Conservation Amendment. Federal Register 1981; 46(11). Westmore GA and Eversden ID: Noise Induced Hearing Loss and Orchestral Musicians. Arch Otolaryngol 1981; 107(12): 761-4. SOURCES OF ADDITIONAL HELP Written and telephone inquiries about health hazards for musicians will be answered by the Information Center of the Center for Safety in the Arts. The Information Center has a variety of written materials available on this subject. Permission to reprint his data sheet may be requested in writing from the Center. Enclose a self-addressed, stamped envelope for our publications list. Write: Center for Safety in the Arts, 5 Beekman Street, New York, N.Y. 10038. Telephone: 212/227-6220 This data sheet has been made possible through funding from the New York State Department of Labor, Occupational Safety and Health Training and Education Program. CSA is also supported with public funds from the National Endowment for the Arts, New York State Council on the Arts and the New York City Department of Cultural Affairs. (c) Copyright Center for Safety in the Arts 1988