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DOI: 10.1055/s-0037-1603759
Self-Assessment Questions
Publication History
Publication Date:
19 July 2017 (online)
This section provides a review. Mark each statement on the Answer Sheet according to the factual materials contained in this issue and the opinions of the authors.
Article One (pp. 226–227) Overview
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Which of the following is not an example of continuous noise, which remains constant and stable over time?
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Boilers in power plants
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Weaving machine in a textile plant
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Nail guns on a construction site
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Newspaper printing press
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Which of the following statements best describes intermittent noise?
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Intermittent noise refers to noise levels that are interrupted by intervals of relatively low sound levels. Intermittent noise will have relatively large fluctuations in level within the period of observation.
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Intermittent noise exposure refers specifically to occupational environments in which broadband noise from machinery is either present or absent.
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Intermittent noise refers to acoustic environments with fluctuating frequency components and peak sound pressure levels ranging from 85 dBA to 115 dBA.
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Intermittent noise exposures are characterized by spectral fluctuations in the noise signal.
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Why has intermittent noise been considered less hazardous to hearing than continuous noise?
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The exchange rate is different for intermittent versus continuous noise.
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The ear may have a chance to recover during quiet periods.
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Inner hair cells are not sensitive to intermittent noise exposures.
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Intermittent noise does not contain impulsive noise components.
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The exchange rate
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is the ratio between A-weighted noise exposures and C-weighted noise exposures
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is used to determine the ratio between peak sound pressure levels and 8-hour time-weighted average noise exposures
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is the relationship between a noise level and the halving or doubling of the amount of time a person can be exposed at that noise level
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has also been referred to as the “time-intensity tradeoff,” the “trading relation,” or the “doubling rate”
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Both C and D
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Auditory synaptopathy is
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a condition that is easily identified with standard audiometric testing
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unlikely to be caused by noise exposure
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the destruction of synaptic connections between hair cells and auditory nerve fibers
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the construction of synaptic connections between hair cells and auditory nerve fibers
Article Two (pp. 227–229) Attempts to Define Non-Gaussian Noise
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Effective quiet has been defined as
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the lowest level of noise that does not lead to permanent threshold shifts in otologically normal young adults
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the highest level of noise that will not interfere with temporary threshold shift recovery
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the level of noise necessary to successfully complete a quantitative task
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the maximum noise level regulated for public libraries
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average noise levels that do not exceed 45 dBA over an 8-hour period
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The beginning of an impulse noise–from the time the noise starts until the noise level first returns to the baseline level–is termed the
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A-duration
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B-duration
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C-duration
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Friedlander wave
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The classic waveform of an impulse or impact noise can change considerably when the sound is measured in an indoor versus an outdoor environment due to
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reverberation and reflection from walls and other interior surfaces
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limitations of sound measuring equipment
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the effects of temperature and humidity on sound transmission
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increased background noise
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Which of the following is an example of impact noise?
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Rifle shots
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A burst of compressed air
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Fireworks
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Hammering
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A chemical explosion
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All other factors remaining constant, which of the following noise environments may be presumed to pose the greatest hazard to hearing?
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Continuous noise averaging 90 dBA
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Intermittent noise averaging 90 dBA
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Impulsive noise superimposed on continuous noise averaging 90 dBA
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Varying noise averaging 90 dBA
Article Three (pp. 229–234) Summary of the Previous Report to the National Institute forOccupational Safety and Health on the Exchange Rate (1992)
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Which exchange rate is most commonly used worldwide?
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3 dB
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4 dB
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5 dB
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6 dB
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In the 1960s, the National Academy of Sciences Committee on Hearing and Bioacoustics (CHABA) based its noise exposure criteria on which of the following?
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Temporary threshold shift measured 2 minutes after cessation of exposure (TTS2) is a consistent measure of the effects of a single day's exposure.
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All exposures producing a given TTS2 will be equally hazardous.
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Noise-induced permanent threshold shift produced after many years of habitual exposure will be the same as the TTS2 produced in normal ears by an 8-hour exposure to the same noise.
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All of the above.
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Why might using a 5-dB exchange rate be underprotective against noise-induced hearing loss?
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Research has shown that a higher exchange rate is more protective than a lower exchange rate.
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Animal models indicate exactly which exchange rate should be used.
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Many of the assumptions on which the 5-dB exchange rate is founded have been called into question.
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Studies involving human subjects have shown that the exchange rate is irrelevant when the ambient noise level is over 100 dBA.
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Which occupation could receive a benefit (i.e., potentially less risk of hearing loss) from intermittent noise exposures?
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Power plant boiler operator
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Forklift driver in a noisy warehouse
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Assembly line worker
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Lumberjack
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According to Passchier-Vermeer's analysis for the 3000-Hz frequency after 15 years of noise exposure:
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The data points for intermittent and varying noise show less hearing loss than those for continuous noise.
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The data points for intermittent and varying noise show roughly the same hearing loss as the curve for continuous noise exposure.
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The data points for intermittent noise show less hearing loss than the continuous noise curve predicts.
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The varying noise data points show significantly more hearing loss than the intermittent noise data.
Article Four (pp. 234–237) Laboratory Investigations Since the 1992 Report
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The findings from Ward's 1991 report on the role of intermittence in permanent threshold shift support which of the following concepts?
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The equal energy hypothesis (i.e., 3-dB exchange rate) is suitable for some noise exposure conditions, but higher exchange rates are more appropriate for several others.
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The equal energy theory was based on uninterrupted exposures for indefinite time periods, such as weeks or months.
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Shorter pauses and shorter durations did not show ameliorative benefits.
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Controlling the duration of noise bursts and pauses were not important in predicting auditory damage.
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In 2004, Harding and Bohne analyzed several studies that show, at least under certain laboratory conditions, that
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rest periods between exposures do not provide significant benefits in terms of cochlear cell loss
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rest periods between exposures can provide significant benefits in terms of cochlear cell loss
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rest periods between exposures demonstrate a simple relationship to the location of damage along the basilar membrane
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rest periods between exposures demonstrate a simple relationship to the time of damage assessment
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An improvement in hearing threshold levels as the noise exposure continues has been referred to as
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threshold shift
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minimal auditory damage
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intermittency
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toughening
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Delayed recovery from temporary threshold shift could have a negative effect on the ear's ability to recuperate between exposures; this would help to explain
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the increase in the damaging potential of impulse/impact noise documented in many investigations
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the increase in linear recovery patterns generated by impulse noise
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the decrease in the damaging potential of impulse/impact noise documented in many investigations
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the decrease in linear recovery patterns generated by impulse noise
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Which of the following is not a reason the chinchilla is often considered as an excellent model for studying the effects of noise on humans?
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Its audibility curve is similar to that of humans in the frequencies at which both species are maximally sensitive.
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The patterns and progression of noise-induced damage appear to be very similar to humans.
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The chinchilla has a long life span, which is convenient for assessing the effects of long exposures.
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Its middle and inner ears are surgically accessible so that it may be rendered monaural.
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The chinchilla appears to be somewhat more sensitive to noise than humans.
Article Five (pp. 237–239) Impulse Noise
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Which of the following statements is true regarding the main difference between impact and impulse noise?
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Impulse noise refers to a sudden reduction in noise levels, and impact noise refers to the high spike in sound levels generated from explosions.
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Impulse noise does not occur under normal atmospheric conditions, and impact noise refers to the high-level energy released in the atmosphere.
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Impulse noise refers to the sudden high-level transient energy released in the atmosphere, and impact noise refers to the collision of two more solid objects.
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Impulse noise is generally above 120-dB sound pressure level, and impact noise is generally less than 120-dB sound pressure level.
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In general, research on both animals and humans has found that noise exposures that contain impact or impulse sounds
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produce an auditory hazard equivalent to broadband continuous noise when broadband noises are measured using A-weighting and impulse or impact sounds are measured using peak sound pressure levels
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usually produce greater damage to the auditory system than exposure to continuous noise
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produce less hearing damage than continuous noise because of their very short durations
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produce a hearing damage risk that is equal to the risk of a continuous noise with an exposure duration long enough to produce an asymptotic threshold shift
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typically produce threshold shifts that, because of the short duration of impulse and impact sounds, recover more quickly than exposures to continuous noise of equivalent sound pressure levels
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What are the main damage-risk metrics used to characterize exposure to impulsive sounds?
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Time-weighted average and noise dose
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Peak sound pressure level and A/B duration as specified by MIL-STD-1474D
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The auditory hazard units as specified in the auditory hazard algorithms for humans model
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An energy-based metric such as the A-weighted equivalent sound level (LAeq) or the LAeq100msec
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A and B are true
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C and D are true
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Impulsive sounds can typically be measured using
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any sound level meter or noise dosimeter
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type 1 sound level meter or type 2 noise dosimeter
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specialized equipment capable of capturing high-level transients
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all of the above
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The importance of the critical level concept in the development of damage-risk criteria is:
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The critical level may vary according to species.
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Delayed recovery is more likely to occur from high levels of intermittent noise than from varying or continuous noise.
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Any adjustment to the exchange rate needs to take into account sound levels that appear to shift the damage mechanism from metabolic to mechanical.
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The critical level in both animals and humans is independent of waveform, spectrum, duration, and repetition rate.
Article Six (pp. 239–249) Complex Noise
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Non-Gaussian (or complex noise) refers to
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noise with an average 8-hour exposure level less than 85 dBA
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occupational noise exposures whose levels have not been filtered to exclude potential electromagnetic interferences
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noise with asymmetrical spectral distribution dominated by frequency components below 1,000 Hz
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noise environments in which the temporal distribution of the noise is not normally distributed or “Gaussian”
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that portion of a 24-hour timeweighted average exposure that includes both recreational and environmental noise but that excludes work-related noise exposures
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Recent animal experiments by Hamernik, Qiu, and others at SUNY Plattsburgh showed that:
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Breaks during the work shift tended to reduce the damaging effects on hearing as long as the LAeq and kurtosis values were the same.
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There was an inverse relationship between hearing damage and kurtosis above β = 50.
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There was no toughening effect with the intermittent pattern the experimenters chose.
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Both cell loss and PTS were independent of the temporal structure of the complex noise so long as the spectral energy and kurtosis values were the same.
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What parameter can be used as a descriptor of noise environments with levels and temporal characteristics that are non-Gaussian?
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Hoarseness
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Timbre
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Squeakiness
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Peakedness
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Repetitiveness
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It is difficult to conduct demographic studies of complex noise in the U.S. mainly because:
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It is difficult to find worker populations that are exposed only to complex noise and not to other kinds of noise.
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Worker populations that have rarely or never used hearing protection devices are very hard to find.
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The exchange rate used by most American companies is the 5-dB, OSHA exchange rate
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It is difficult to find workers exposed primarily to continuous noise to use as control populations.
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The principal finding from the studies by the U.S./China team was:
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The same prevalence of hearing loss occurred among workers exposed to continuous noise and complex noise so long as the complex noise was adjusted for kurtosis.
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The textile workers exposed to continuous noise had more hearing loss because they had more years of exposure.
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The metal fabrication workers benefited from the intermittencies characteristic of their type of work.
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The fact that the Chinese population had been carefully screened reduced the differences between the two types of exposures.
Article Seven (pp. 249–256) Neurological Investigations of the Auditory System
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The term synaptopathy as applied to the ear can be associated with
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pathogenic lesions on the external auditory meatus
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fusion of the stapes to the cochlear wall
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loss of spiral ganglion neurons and their synapses
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loss of inner hair cells while outer hair cells remain intact
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The term hidden hearing loss is used to describe
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malingering
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hearing thresholds of 20 dB hearing loss
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a gap between the air conduction and bone conduction thresholds of less than 10 dB
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disorders that affect suprathreshold perception without loss of threshold sensitivity.
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Based upon recent studies of auditory synaptopathy resulting from noise exposure, which of the following is thought to be true?
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Damage to hearing appears to continue after the cessation of noise exposure.
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Noise exposure appears to exacerbate the effects of aging.
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Normal hearing threshold levels do not signify an absence of damage to the auditory system.
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Current noise exposure guidelines and diagnostic procedures for identifying noise-related damage may need to be re-evaluated.
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All of the above are true.
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Why have the adverse effects of auditory synaptopathy not been investigated until this decade?
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Spiral ganglion cells can survive for years despite the loss of their connection with hair cells.
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The synaptic terminals of these nerve fibers are unmyelinated and are therefore difficult to see with traditional microscopy and staining techniques.
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Neuronal degeneration is selective for cochlear nerve fibers with high thresholds.
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All of the above are true.
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Which of the following recent scientific developments may be relevant in considering future noise standards?
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New instrumentation capable of integrated noise measurements
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New metrics for the characterization of non-Gaussian noise
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New imaging for quantifying changes to inner hair cells and spiral ganglion synapses
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New audiological tests for the evaluation of central auditory function
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All of the above
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