Prevention of Noise-Induced Hearing Loss from Recreational Firearms

Abstract

In the United States and other parts of the world, recreational firearm shooting is a popular sport that puts the hearing of the shooter at risk. Peak sound pressure levels (SPLs) from firearms range from ∼140 to 175 dB. The majority of recreational firearms (excluding small-caliber 0.17 and 0.22 rifles and air rifles) generate between 150 and 165 dB peak SPLs. High-intensity impulse sounds will permanently damage delicate cochlear structures, and thus individuals who shoot firearms are at a higher risk of bilateral, high-frequency, noise-induced hearing loss (NIHL) than peer groups who do not shoot. In this article, we describe several factors that influence the risk of NIHL including the use of a muzzle brake, the number of shots fired, the distance between shooters, the shooting environment, the choice of ammunition, the use of a suppressor, and hearing protection fit and use. Prevention strategies that address these factors and recommendations for specialized hearing protectors designed for shooting sports are offered. Partnerships are needed between the hearing health community, shooting sport groups, and wildlife conservation organizations to develop and disseminate accurate information and promote organizational resources that support hearing loss prevention efforts.

Full text

Prevention of NIHL from Recreational Firearms 1
Title: Prevention of Noise-Induced Hearing Loss from Recreational Firearms
Deanna K. Meinkea
Donald S. Finana
Gregory A. Flammeb
William J. Murphyc
Michael Stewartd
James Lankforde
Stephen Taskob
a University of Northern Colorado, Audiology and Speech-Language Sciences, Greeley, CO, USA
b Western Michigan University, Department of Speech Pathology and Audiology, Kalamazoo, MI, USA
c National Institute for Occupational Safety and Health, Division of Applied Research and Technology,
Cincinnati, Ohio, USA
d Central Michigan University, Department of Communication Disorders, Mount Pleasant, MI, USA.
e Northern Illinois University, Allied Health and Communication Disorders, DeKalb, IL, USA.
Key Words
Impulse noise, firearms, noise-induced hearing loss, hearing loss prevention, hearing
conservation, hearing protection
Objectives:
 Identify acoustic and behavioral factors that influence the risk of auditory damage from
recreational firearm impulse noise exposures

Prevention of NIHL from Recreational Firearms 2
 Describe hearing loss prevention strategies for individuals exposed to impulse noise from
recreational firearms.
Disclaimer: The findings and conclusions in this report are those of the authors and do not necessarily
represent the views of the National Institute for Occupational Safety and Health.
Correspondence to:
Deanna K. Meinke, Ph.D.
University of Northern Colorado, Gunter Hall 1500, Campus Box 140, Greeley, CO 80639
Email: Deanna.Meinke@unco.edu
Abbreviations
ANSI: American National Standards Institute
dB: decibel
fps: feet per second
HFHL: high-frequency hearing loss
HPD: hearing protection device
Hz: hertz
LFHL: low-frequency hearing loss
ms: millisecond
NHANES: National Health and Nutrition Examination Survey
NIHL: noise-induced hearing loss

Prevention of NIHL from Recreational Firearms 3
NIOSH: National Institute for Occupational Safety and Health
NITS: noise-induced threshold shift
NRR: noise reduction rating
TTS: temporary threshold shift
SPL: sound pressure level
U.S.: United States

Prevention of NIHL from Recreational Firearms 4
Abstract
Recreational firearm shooting is a popular sport worldwide that puts the hearing of the
shooter at risk. Peak sound pressure levels (SPL) from firearms range from approximately 140 to
175 decibels (dB). The majority of recreational firearms (excluding small caliber .17/.22 rifles and
air rifles) generate between 150 and 175 dB peak sound pressure level at the shooter’s ears. High
intensity impulse sounds will permanently damage delicate cochlear structures. Individuals who
shoot firearms are at a higher risk of bilateral, high-frequency, noise-induced hearing loss (NIHL)
than peer groups that do not shoot. Several factors influence the risk of NIHL including; the use
of muzzle brakes, the number of shots fired, the distance between shooters, the shooting
environment, the choice of ammunition, the use of a suppressor, and hearing protection fit and use.
Prevention strategies that address these factors and recommendations for specialized hearing
protectors designed for shooting sports are offered. Partnerships are needed between the hearing
health community and shooting sport and wildlife conservation organizations to develop and
disseminate accurate information and promote organizational resources that support hearing loss
prevention efforts.

Prevention of NIHL from Recreational Firearms 5
Millions of individuals, across all ages, shoot firearms for sport. Recreational hunting or
target shooting presents the most serious and immediate threat to hearing when compared to
other leisure activities. Participation in firearm-related sport jeopardizes not only the hearing of
the shooter but also others nearby (instructors, spectators, athletes). Although the potential for
auditory damage from high-level impulse noise has been recognized for over a century, our
understanding of the magnitude of the firearm-related risk, factors influencing the risk, and
effective strategies to prevent hearing loss and tinnitus – ringing or buzzing in the ears -
continues to advance.
RECREATIONAL SHOOTING
Civilians are estimated to own approximately 650 million firearms worldwide.1 Firearms
are used for sport while hunting, target-shooting, competitive-shooting, reenacting historical
events, entertaining, fundraising, scouting, and officiating in athletic events (i.e., track and field,
swimming). It is estimated that approximately 46% of adult males and 13% of adult females
have reported firing a gun at some point in their life (Flamme, G.A., unpublished analysis of data
from the 2007 U.S. National Health Interview Survey). The number of individuals participating
in firearm-related sports varies as a function of sport classification, geographical region and
tradition or culture. It is estimated that 83 to 97 civilian firearms per 100 persons are owned in
the U.S.1 and many are used for hunting purposes. In 2015, 14.8 million hunting license holders
purchased permits in the U.S.2 In 2010, 1.7 million youths were hunters.3 Over 20 million
Americans participated in target-shooting related activities in 2011.4 Target shooting activities
can be described as; plinking (informal), sighting-in, training-related, equipment-related
(ammunition, weapon), sporting clay/skeet/trap, tactical and competitive. Increases in the
number of US women engaged in firearm-related sports were found between 2001 and 2013.5

Prevention of NIHL from Recreational Firearms 6
The number of female hunters increased from 1.8 to 3.5 million (85% increase) and women
target shooters increased from 3.3 to 5.4 million (60% increase). Recreational shooting begins
early in life. A survey of Colorado and Michigan youth who hunt, revealed that 57% of the youth
began to shoot before the age of 8 years.6 Geographically, the International Practical Shooting
Confederation (IPSC) exemplifies the global popularity of dynamic target sport shooting with six
worldwide geographical zones (African, Australasian, European, Pan-American, North
American, and South American) and 100 national affiliates hosting shooting events at least
annually. Regardless of the setting or the sport, it is the gunshot that poses the hazard to hearing.
THE “BANG”
Once the trigger is pulled, a chain of events leads to the physical generation of a high-
frequency, short-duration impulse waveform perceived by human ears as a single “bang” or
“gunshot” (see illustration in Rasmussen et al., 2008).7 The waveform is generated by the firing
pin hitting the cartridge, detonating the primer, which then combusts the gunpowder. The
gunpowder combustion produces a large volume of gas, and the resultant pressure accelerates the
projectile down the barrel of the gun, where it exits the muzzle. Some projectiles travel at
supersonic speeds, producing a conical shock wave or miniature sonic boom, commonly called
an N-wave, that expands outwards from the location of the projectile tip, similar to the wake
produced by a motorboat in the water. Once the hot compressed gases are released, a spherical
blast wave initially centered on the muzzle will be produced. Turbulent airflow around and in
front of the muzzle is created as the gas is ejected forward. Outdoors, in a non-reverberant
environment, the duration of the recreational gunshot is extremely brief, typically less than 10
ms.

Prevention of NIHL from Recreational Firearms 7
Accurate acoustic measurement of a gunshot requires specialized hardware and software
that is able to capture the rapid rise time and extreme magnitude of the pressure changes from
ambient, to peak, and back to ambient, air pressure. A small diameter precision microphone with
sufficient dynamic range and frequency response should be used to accurately record the
impulse. A data acquisition system incorporating a high sampling rate is also necessary to
preserve the details of the impulse waveforms. High quality impulse recording allows the
detailed resolution and analysis of the impulse waveform that permits identification of the
different source mechanisms and quantification of auditory risk.7 The acoustic characteristics of
the recreational firearms subsequently described in Table 1 below were each measured by the
authors using this type of instrumentation rather than commercial or laboratory grade sound level
meters.
The maximum peak sound pressure levels (SPL) from firearms range from
approximately 140 to 175 decibels (dB).7-13 The majority of recreational firearms (excluding
small caliber .17/.22 rifles and air rifles) generate between 150 and 175 dB peak SPL. The
general range of peak SPLs measured at the left ear of a right-handed shooter for various
categories of recreational firearms are summarized in Table 1. 7-12 Pistols have shorter barrel
lengths than rifles and shotguns and rank high in peak SPL due in part to the closer proximity of
the muzzle to the ears. Shorter barrel lengths found in both youth firearms11 and semi-automatic
rifles14 also increase the SPL measured at the shooter’s left ear. The left ear is reported due to the
higher asymmetrical exposure from a rifle or shotgun gunshot and higher prevalence of hearing
loss in the left ear of right-handed shooters, as addressed later in this manuscript.

Prevention of NIHL from Recreational Firearms 8
Table 1. Rank-ordered range of mean unweighted peak sound pressure levels for recreational
firearms measured at the left ear of a right-handed shooter.7-12
Recreational Firearm Type
Peak Sound Pressure Level
(dB)
Rifles (higher caliber than .22)
~159-174
Pistols (higher caliber than .22)
~148-171
Shotguns
~152-170
Starter Pistols (blanks)
~148-165
Pistols (.22 caliber)
~155-158
Rifles (.17 and .22 caliber)
~140-144
Air Rifles
~117-134
Non-shooters, or those in close proximity to the shooter (e.g. instructors, spectators,
athletes or other nearby shooters) can experience high-level exposures to impulse noise from
recreational firearms. Flamme et al. measured the peak SPLs from 15 recreational firearms at the
position of a bystander located 1 meter to the left of the shooter in an outdoor environment.
Instantaneous peak levels ranged between 149 and 167 dB and were considered to be unsafe
exposures for the bystanders.15 Athletes and spectators near officials firing starter pistols are also
at an elevated risk of noise-induced hearing loss (NIHL).10 The use of electronic starting devices
for signaling the start of athletic events may minimize auditory risk.
As Kardous et al. point out, there is no universally accepted standard method for
measuring impulse noise.16 Readers are cautioned to critically evaluate the peak sound pressure
levels that are measured/reported using conventional sound level meters, including those adapted
for impulse noise measurements (e.g. ¼ or ⅛ inch microphones, peak setting, impulse setting)

Prevention of NIHL from Recreational Firearms 9
due to limitations related to the microphone sensitivity, temporal
constants, filter effects, voltage supply, analog-to-digital
sampling rate and output/display mode.17-18 Meinke et al.
compared rifle gunshot peak sound pressure levels from four
commercial sound level meter models marketed specially for
impulse noise measurements to a gold-standard research
measurement system.18 The researchers concluded that the use
of a commercial sound level meter utilized for firearm impulse
noise measurements may underestimate auditory hazard for
impulse sound levels at or above approximately 150 dB peak
SPL. Noise dosimeters are known to have similar constraints in
terms of accuracy due to microphone and electronic circuitry
limitations for high level impulses from weapons.16 Noise
dosimeters and commercial sound level meters “clip” the peak pressure measurement when
impulses exceed the dynamic range maxima (typically 150 dB or less) of the instrument, and
incorrectly report the clipped (underestimated) value as the peak SPL.19
In the past, these conventional sound level measurement limitations have likely
contributed to the ceiling limit of 140 dB SPL referenced on “noise thermometers” used for
educational purposes. Ideally, contemporary educational materials, info-graphics and counseling
tools should be updated to consistently reference evidence-based unweighted peak sound
pressure levels when communicating the auditory risk from recreational firearms to the public. A
few examples of correctly referenced firearm levels in noise thermometers are provided in the
sidebar.
3M:
http://multimedia.3m.com/m
ws/media/1074386O/decibel-
scale-noise-meter.JPG
Dangerous Decibels:
http://dangerousdecibels.org/
education/information-
center/decibel-exposure-time-
guidelines/
Howard Leight:
http://www.howardleight.com
/hearing-protection/noise-
thermometer
NOISE
THERMOMETERS

Prevention of NIHL from Recreational Firearms 10
AUDITORY RISK FROM FIREARM IMPULSE NOISE
Quantifying the actual risk to the auditory system based upon the acoustic characteristics
of the impulse noise is complex. Contemporary damage risk criteria (DRC) have been
categorized into three types: impulse waveform parameter-based, total energy within the
impulse, and theoretical ear-based electroacoustic models of the auditory system.20, 21 Waveform
parameter-based DRC are typically quantified in terms of the peak amplitude, pressure wave and
envelope duration of the impulse.22 Other damage risk criteria reference the energy-based,
integrated A-weighted 8-hour equivalent level (LeqA8), 23-25 apply criteria derived from theoretical
physiologically based ear-models (e.g. the Auditory Hazard Assessment Algorithm for
Humans)26, or apply fatigue modeling to cochlear structure damage predictions.27 These more
complex approaches are typically utilized for research or military purposes and, once validated
fully, could better inform healthcare providers and the public. The peak sound pressure level
(SPL) measured at the ear level of the shooter is commonly referenced for quantifying auditory
risk for clinical applications and educational interventions.
Definitive impulse noise risk limits for the human ear are also difficult to determine due
to the safety considerations that limit present day human research into this area. Consequently,
animal studies utilizing the chinchilla (and other animal models) have been relied upon to
explore the relationship between impulse noise exposure and hearing loss.28-31 Henderson and
Hamernik31 determined that the critical boundary for impulse noise exposure for the chinchilla is
about 140 dB peak SPL, but noted that the risk boundary is ultimately dependent upon the actual
waveform characteristics. Research evidence also suggests that impulse noise is more damaging
than continuous noise and that recovery is prolonged and less complete.28-31 Chan, Ho and

Prevention of NIHL from Recreational Firearms 11
Ryan30 have modeled human recovery from temporary threshold shift measured at 2 minutes
(TTS2) post exposure using chinchilla auditory brainstem response data. The recovery window
for a 25 dB TTS2 is predicted to be within 43 hours with a longer full recovery time for a 50 dB
TTS2 extending out to approximately 38 days. Ultimately, four acoustic parameters of the noise
source interact and determine the resulting hearing loss: 1) type of noise (continuous,
impulse/impact, blast), 2) sound pressure level, 3) duration and temporal pattern of the exposures
(how long and how often), and 4) spectral composition.32 More recently, there has been a
growing interest in waveform kurtosis, a statistical measure of the relative peakedness or flatness
of the noise distribution, which may also be useful in predicting hearing damage from impulse
signals.28,33,34 The acoustic characteristics of a gunshot from a recreational firearm are generally
described as impulsive, peak SPL greater than 140 dB, brief duration (<10 ms outdoors), and
high frequency, with spectral peaks between 400 and 2000 Hz.
There are no mandated impulse noise regulations imposed on recreational firearm
shooters. The World Health Organization (WHO) recommends peak sound pressure levels not
exceed 140 dB for adults and 120 dB for youth.35 The U.S. Occupational Safety and Health
Administration,36 and the National Institute for Occupational Safety and Health USA37
incorporate a peak limit of 140 dB SPL for occupational noise exposures. The European Union
incorporates a C-weighted peak limit of 137 dB SPL in recommended guidelines for adult
workers.38 All of the rifles, pistols and shotguns measured in Table 1 exceed these peak SPL
limits for both adults and children. The majority of the air rifles, with the exception of the Gamo
Whisper pellet gun and the Daisy Red Ryder BB gun, exceeded the 120 dB peak SPL limit for
youth, while none exceeded the 140 dB peak SPL limit for adults. Without mandated noise

Prevention of NIHL from Recreational Firearms 12
limits, the organizations sponsoring shooting events and the individuals participating in or
attending the events are responsible for hearing loss prevention.
HEARING LOSS FROM FIREARM IMPULSE NOISE
As early as 1860, Toynbee recognized the pattern of asymmetrical high-frequency
hearing loss in patients shooting firearms for sport.39 He also recognized the distinction between
immediate hearing loss and tinnitus following shooting and gradual onset noise-induced hearing
loss that was attributed to repeated exposures to impulse noise over time.40 Today, it is readily
accepted that unprotected noise exposure from firearms can lead to permanent NIHL, as a result
of direct mechanical damage or secondary physiological and biochemical inner ear effects from
repeated gunshot exposures over time or from a limited number (including a single shot) of high
intensity exposures termed “acoustic trauma”. Tinnitus is also a consequence of firearm noise
exposure and should be considered an early warning sign of over-exposure.6,41,42
The prevalence of bilateral high-frequency NIHL in sports shooters has been estimated
by numerous epidemiological and experimental studies over the years, comparing audiometric
data from groups of individuals who engage in recreational shooting with a matched group who
do not shoot for sport.43-46,63 Sport hunters (n=103) were found to have significantly worse
hearing thresholds at 3-8 kHz (especially at 6 kHz) when compared to physician non-hunters
(n=21) for all age groups.43 Left ear hearing thresholds were significantly poorer than right ear
thresholds. Updike and Kramer found significantly poorer hearing at 2, 3, 4, and 6 kHz when
comparing the hearing thresholds of 60 recreational shooters with age-matched, non-shooting
individuals.44 The greatest differences were found at 4 and 6 kHz, and left ears were poorer than
right ears. Older shooters had significantly greater hearing loss than younger shooters. Nondahl

Prevention of NIHL from Recreational Firearms 13
et al. reported a low prevalence of recreational firearm use among women, both for target
shooting (ever, 3.3%; past year, 0.1%) and hunting (ever, 11.3%; past year, 0.5%).45 Male
prevalence for hunting (ever, 74.9%; past year, 21.2%) was higher than the prevalence of target
shooting (ever, 15.6%; past year, 4.8%). Therefore, hearing threshold outcomes from males only,
aged 48 to 92 years, who participated in baseline hearing tests (n=1538) as part of a larger
Epidemiology of Hearing Loss Study were reported. A high-frequency hearing loss was defined
as a pure-tone average of hearing thresholds at 4, 6 and 8 kHz greater than 60 dBHL in the worse
ear, in an effort to differentiate those with greater hearing loss and account for any asymmetry
between ears. A history of target shooting and hunting were each associated with “marked” high
frequency hearing loss in men after adjusting for age and other factors. Hunting increased the
risk of having a severe high frequency hearing loss, by 7% for every 5 years the men had hunted.
The most relevant current U.S. epidemiological hearing data is based upon a comparison
of audiometric data from the recent National Health and Nutrition Examination Survey
(NHANES) 2011-2012 cycle to the 1999-2004 NHANES cycle for 20-69 year olds.46 The
authors report that the overall prevalence of unilateral and bilateral speech-frequency hearing
loss significantly decreased from 15.9% (28 million) to 14.1% (27.7 million) after adjustment for
age and sex. Firearm use (recreational, job, or military) was reported by 45.7% of the population
with 32.6% shooting <1000 lifetime rounds and 12.9% shooting ≥1000 lifetime rounds. The
prevalence of both speech-frequency and high-frequency hearing impairment as related to
firearm use is provided in Table 2. The prevalence of high-frequency hearing loss (37.1%) is
greater than the prevalence of speech-frequency hearing loss (17.3%) in firearm users. When
considering speech-frequency hearing impairment, bilateral hearing impairment (10%) is only
slightly more prevalent than unilateral impairment (7.3%). However, differences in bilateral

Prevention of NIHL from Recreational Firearms 14
(24.8%) versus unilateral impairment (12.3%) are much larger for high-frequency hearing
impairment. Bilateral hearing impairment is also more common than unilateral impairment when
considering the number of lifetime rounds fired. Left versus right ear differences (asymmetry)
were not analyzed separately in that study.
Table 2. Prevalence of Hearing Impairment Related to Firearm Use, US Adults Aged 20-69
years, NHANES, 2011-2012*
Firearms, including use
for recreation, job, or
military
(NHANES 2011-2012)
US Adults aged 20-69 yrs
Prevalence, %
Speech-Frequency Hearing Impairmenta, %
(95% CI)
Overallc
Unilaterald
Bilaterale
Not Used
54.3
11.4 (9.1-14.2)
6.0 (4.5-8.0)
5.4 (4.3-6.8)
Yes Used
45.7
17.3 (13.6-21.9)
7.3 (5.7-9.5)
10.0 (7.3-13.6)
<1000 lifetime rounds
fired
32.6
14.0 (10.6-18.2)
6.0 (4.2-8.4)
8.0 (5.8-10.9)
≥1000 lifetime rounds
fired
12.9
26.0 (19.7-33.4)
10.8 (8.4-13.7)
15.2 (9.4-23.6)
High-Frequency Hearing Impairmentb, %
(95% CI)
Overallc
Unilaterald
Bilaterale
Not Used
54.3
25.9 (23.5-28.6)
11.6 (10.1-13.2)
14.4 (12.7-16.3)
Yes Used
45.7
37.1 (31.9-42.6)
12.3 (9.4-15.9)
24.8 (20.6-29.5)
<1000 lifetime rounds
fired
32.6
32.2 (26.8-38.2)
10.2 (6.3-15.9)
22.1 (17.6-27.4)
≥1000 lifetime rounds
fired
12.9
49.7 (40.2-59.2)
18.0 (13.1-24.2)
31.7 (22.5-42.6)
Note: Adapted from Hoffman, Dobie, Losconczy, Themann and Flamme, 2016.46
aSpeech-frequency hearing impairment is defined as PTA of thresholds at 0.5, 1, 2, and 4 kHz
greater than 25 dBHL.
bHigh-frequency hearing impairment is defined as PTA of thresholds at 3, 4 and 6 kHz greater
than 25 dBHL.
cOverall refers to the sums of unilateral and bilateral hearing impairment, which means hearing
loss in one or both ears.
dUnilateral refers to the pure-tone average in only 1 ear exceeds 25 dBHL.
eBilateral refers to the pure-tone average in both ears exceed 25 dBHL.

Prevention of NIHL from Recreational Firearms 15
The prevalences of bilateral (better-ear) speech-frequency hearing impairment and
bilateral (better ear) high-frequency hearing impairment, and higher odds ratios related to firearm
use are summarized in Table 3, including relevant adjustments for all hearing impairment risk
factors (age, sex, race/ethnicity, educational level, smoking, hypertension, diabetes, occupational
noise exposure, and non-occupational noise exposure).46 Heavy use of firearms (≥1000 rounds
fired) significantly increased the risk of speech-frequency hearing impairment in both the better
and worse ears (unadjusted odds ratio, 3.7: 95% CI, 1.7-5.7). When considering all of the noise
exposure variables, firing 1000 or more lifetime rounds retains a statistically significant
association (OR, 1.8; 95% CI, 1.1-3.0) and further emphasizes the public health risk that firearm
use presents to the avid shooter’s hearing.
Table 3. Prevalence of Bilateral (Better Ear) Hearing Impairment Related to Firearm Use, US
Adults Aged 20-69 years, NHANES, 2011-2012*
Hearing
Impairment
Firearms, including use
for recreation, job, or
military
(NHANES 2011-2012)
US Adults aged 20-69 yrs
Prevalence, %
(95% CI)
Odds Ratio (95% CI)
Unadjusted
Adjusted for
Age and Sex
Adjusted for
All Variables
Bilateral
(Better Ear)
Speech-
Frequency
Impairment
None
5.4 (4.3-6.8)
1[Reference]
1[Reference]
1[Reference]
<1000 lifetime rounds
fired
8.0 (5.8-10.9)
1.5 (1.1-2.1
1.4 (0.9-2.1)
1.4 (0.8-2.2)
≥1000 lifetime rounds
fired
15.2 (9.4-23.6)
3.1 (1.7-5.7)
2.4(1.4-4.2)
1.8 (1.1-3.0)
Bilateral
(Better Ear)
High-
Frequency
Impairment
None
14.4 (12.7-16.3)
1[Reference]
1[Reference]
1[Reference]
<1000 lifetime rounds
fired
22.1 (17.6-27.4)
1.7 (1.3-2.2)
1.4 (0.9-2.1)
1.2 (0.9-1.9)
≥1000 lifetime rounds
fired
31.7 (22.5-42.6)
2.8 (1.6-4.7)
1.5 (1.0-2.5)
1.3 (0.7-2.3)
* Adapted from Hoffman, Dobie, Losconczy, Themann and Flamme, 2016.46

Prevention of NIHL from Recreational Firearms 16
Young adults or youth who shoot firearms are also at risk of NIHL. High frequency
hearing loss and a notched audiometric configuration, especially at 6 kHz, is associated with
recreational firearm use in 10-20 year olds.47-49 Henderson et al. investigated trends in noise-
induced threshold shifts (NITSs), high frequency hearing loss (HFHL) and low frequency
hearing loss (LFHL) in youth aged 12-19 years using audiometric data from NHANES in 1988-
1994 and 2005-2006.50 The 2005-2006 data set also included participant interview responses
regarding whether they had ever used firearms. Overall, there were no significant increases in
rates of NITSs, HFHL, or LFHL between the two time periods. The prevalence of NITS in one
or both ears was 15.9% and increased to 16.8% and the prevalence of HFHL was 11.1% and
increased to 12.9%. Gender differences in the prevalence of NITS were evident in the 1988-1994
data set (20.2% male, 11.6% female). However, by 2005-2006, female youth exhibited a
significantly greater increase in the rate of NITS and had similar prevalence rates to males (17%
male, 16.7% female). Female youth had lower prevalence rates for firearm use (42.4% male,
15.1% female). The use of firearms was not associated with a significant increase of NITS (OR,
1.43; 95% CI, 0.94-2.17) in a multivariable model adjusted for age, gender, race/ethnicity and
poverty/income ratio. Interestingly, firearm users were more likely to report using hearing
protection regularly than other youth. The authors did not report independent prevalence rates for
HFHL or LFHL in relation to firearm use.
Clark estimated that 50% of U.S. industrial workers are exposed to gunfire noise from
hunting or target shooting.51 Several studies have considered the additional contribution of
recreational firearm noise exposure to occupational hearing loss in workers with equivalent
occupational noise exposure. Significantly poorer high frequency hearing has been reported in
blue collar, manufacturing workers, railway workers, forestry workers, construction workers,

Prevention of NIHL from Recreational Firearms 17
miners, and farmers who use firearms, compared to respective cohorts who do not shoot.52-62
Johnson and Riffle noted that hearing loss was 9-16 dB poorer at 3, 4, and 6 kHz for male
workers with a positive history of shooting.53 Forestry workers with exposure to firearm
impulses had 9 dB greater hearing loss at 4 kHz and 10 dB greater at 8 kHz than those with low
exposure to shooting impulses.58 No significant differences in hearing were evident for the small
number of female shooters, and the authors attributed this to females primarily shooting small
caliber (.22) firearms as compared to the larger caliber firearms used by the males in the study.
Over 90% of farmers report firearm use.61 Years of hunting and target shooting were associated
with high-frequency hearing loss in farmers (n=1568) by Humann in 2011.62 Becket et al.
considered hearing impairment using binaural ratings in farm workers.57 Years of hunting (but
not target shooting) was associated with hearing impairment which increased 0.16% per year of
hunting. For construction workers that shoot, it is not only the firearm use that puts them at risk
of NIHL, but also their frequent participation in other, non-occupational noise-hazardous
activities that increases their risk when compared to construction workers that do not shoot.59
Chung, Gannon and Willson noted the presence of asymmetrical hearing thresholds in workers
who shot firearms.52
Asymmetry (5-30 dB) in hearing thresholds between the ear ipsilateral to the firearm and
contralateral to it may be evident (Figure 1). The ipsilateral ear is the right ear of a right-handed
shooter and, typically, the hearing loss is worse for the contralateral (left) ear. Taylor and
Williams noted the left ear was 26 dB worse at 3, 4 and 6 kHz in hunters and only 4 dB worse in
the control subjects.43 Chung et al. noted that 13% of workers shouldered their weapon on the
left shoulder and asymmetry in pure-tone thresholds were significant at 2-8 kHz for shooters
with ≥ 10 years shooting history.52 Sataloff compared the hearing loss between ears in left- and

Prevention of NIHL from Recreational Firearms 18
right-handed shooters using rifles or shotguns. He noted that 60% of the left-handed shooters had
more hearing loss in their right ear and 66% of the right-handed shooters had more hearing loss
in the left ear.63 Agnew postulated that the asymmetrical hearing loss is due to the nature of the
placement of the firearm when shooting.64 The “shouldering” of the firearm differs between right
and left-handed shooters when shooting rifles and shotguns.
Figure 1. Example of an asymmetrical noise-induced hearing loss for a 50 year-old male who
shoots recreational firearms.
A right-handed shooter will position the stock of the rifle or shotgun on the right shoulder
and a left-handed shooter will position the stock on the opposite shoulder. This position tilts the
head and results in exposure differences across ears due to the head-shadow effect. For a right-
handed shooter, the head is tilted toward the right shoulder and the left ear is angled forward,

Prevention of NIHL from Recreational Firearms 19
closer to the muzzle blast. Figure 2 illustrates the peak SPL differences simultaneously recorded
at each ear with and without the head in place. Gunshots were generated with a Winchester
model 43 rifle firing a .22 hornet cartridge by a right-handed shooter. A difference of 9.8 dB is
evident and attributed to diffraction of the impulse by the head for the left ear, and shadowing by
the head and shoulder for the right ear, without consideration for any potential effects of hearing
protector attenuation. These measurements clearly support a difference in exposure between the
two ears that may translate to asymmetrical hearing loss. However, the degree of asymmetry may
vary with gun type, the use of hearing protection, and other directional and non-directional noise
exposures over time. A pistol shooter typically holds the firearm with both hands in a centered
position and the head-shadow effect is minimized. There may be other factors that influence the
(a)symmetry of hearing loss, including: years of shooting63, number of rounds fired54, eye
preference for shooting65, and physiological differences between ears.58,65,66

Prevention of NIHL from Recreational Firearms 20
Figure 2. Illustration of head-shadow effect contrasting sound pressure levels measured for each
ear for a right-handed rifle or shotgun shooter.
THE DEMAND FOR AUDIBILITY
All recreational shooters, including those with hearing loss, demand audibility while
engaged in their sport. Interpersonal speech communication is critical for establishing logistical
plans, conveying instruction, and ensuring general safety, such as hearing a warning message or
voice commands from a fellow shooter or range-master. Hearing is needed to monitor the
firearm assembly and function to determine if the action is fully engaged, a cartridge is loaded in

Prevention of NIHL from Recreational Firearms 21
the chamber, the hammer is set, a spent shell is ejected, or a safety mechanism activated. Hearing
may also be used to recognize the timing of target launch and register the accuracy of a shot in
terms of hearing the projectile physically impact the target. For hunters, the demand for auditory
situational awareness extends to localizing the sound of wildlife (especially at a distance),
monitoring the sound of their own body movements during silent approach, detecting hunting
dog barks or beeper collar signals when “on point”, and calling to waterfowl and wildlife.
Strategies to prevent noise-induced hearing loss and tinnitus must be considered in the context of
the audibility demands of the shooter. Fortunately, the value of hearing appears obvious to
individuals experienced in shooting sports and the need to motivate them to protect their hearing
is usually already established within the context of being physically safe and successful at their
sport. For younger or novice shooters, it isadvantageous to counsel them regarding the value of
their hearing as it relates to their general safety, firearm safety, and sport performance.
FACTORS THAT INFLUENCE THE RISK OF NIHL
Regardless of the sport, the use of hearing protection is essential. However, there are
additional strategies that can be implemented to prevent noise-induced hearing loss and tinnitus
from firearm use.

Prevention of NIHL from Recreational Firearms 22
Muzzle brakes (ports) are utilized to
counter the physical effects of recoil (kickback)
when a gun is discharged by redirecting the
propellant gases perpendicularly relative to the
barrel through slots, vents, holes or baffles
positioned at the end of the muzzle. The use of
muzzle brakes increases the noise hazard since
the escaping gases are ejected closer to the ear
and radiates more sound pressure backwards
toward the shooter which increases the exposure
measured at the shooters ear.15
The number of shots fired without
hearing protection increases the risk of NIHL.
Small game and waterfowl hunters may be at
greater risk of NIHL due to shooting hundreds of
rounds per season, in comparison to large game
hunters who may only fire their rifle a few times
during the season.42 Target shooters and
competitive shooters also increase their risk
dependent upon their choice of caliber/gauge and
the number of shots fired. Shooting in groups
increases the auditory hazard to the ears of the
shooter, since the exposures come from both
Always wear well-fit earplugs and/or
earmuffs when shooting or when
positioned near others who are
shooting*
Avoid the use of muzzle brakes (ports)
Reduce the number of shots fired
Shoot smaller cartridge/gauge firearms
when possible
Shoot firearms with longer barrel lengths
when possible
Avoid shooting in groups, and if
necessary, increase distance between
shooters.
Avoid firing simultaneously with other
nearby shooters
Shoot outdoors or in a sound-treated
indoor environment
Avoid shooting over hard reflective
surfaces such as benches or tabletops
Shoot sub-sonic or low-velocity (<1120
fps) ammunition when feasible
Utilize a suppressor
*The use of hearing protection is still
warranted even when implementing the
other listed strategies.
STRATEGIES TO PREVENT HEARING
LOSS WHEN SHOOTING
RECREATIONAL FIREARMS

Prevention of NIHL from Recreational Firearms 23
their own firearm and from other, nearby shooters.9 Increasing the distance between shooters and
minimizing the number of shots fired reduces the risk of NIHL. Shooting at ranges during “off-
hours” may also lower the number of impulse exposures from nearby shooters.
Shooting in an enclosed, reflective, reverberant environment (indoors or hunting blind)
increases the hazard to hearing.21,67 Hunting blinds are used to decrease the chances of visual
detection and may inadvertently increase noise exposure, especially if the muzzle of the firearm
is within the blind allowing the muzzle blast to reverberate inside the blind. For historical
reenactments or entertainment purposes, the shooting environment may be intentionally designed
to replicate a scene, while neglecting the acoustic implications. Shooting from a bench or over a
table also increases the peak SPL reaching the shooter’s ear.11 Design considerations and
acoustical treatments for indoor shooting ranges can help minimize the auditory risk.68-70
Recreational shooters should be encouraged to shoot outdoors and, if shooting indoors,
counseled to select ranges with acoustical treatments that help minimize the risk. Spectators
should be located at sufficient distances to lower the peak levels below 140 dB and below 120
dB if children are present. Technological advancements in sports filming and projection may
provide spectators with close-up viewing from a distance at shooting events.
Ammunition containing less propellant decreases impulse level. Small differences in peak
SPL can be measured across most kinds of loads for recreational firearms.8,11 Subsonic or low-
velocity ammunition (velocity less than 1120 feet per second (fps)) contains a lower propellant
charge and lessens the speed of the projectile, eliminating the noise source caused by the
supersonic flight of the projectile breaking the sound barrier once it leaves the barrel. Firing
ammunition labeled as subsonic or low-velocity less than 1120 fps, can lower peak SPL level
measurements by 10 or 15 dB.71 For hunters, the choice of ammunition is less flexible than for

Prevention of NIHL from Recreational Firearms 24
target shooters. The cost of ammunition may also be inversely related to the number of shots
fired, with more expensive ammunition being used less often.
A firearm suppressor is designed to reduce the sudden release of pressure from the
escaping gases (noise) by coupling a large-volume chamber to the muzzle of the firearm. Baffles
within the chamber act to diffuse the energy of the blast wave propelling the projectile, and
reduce the sound levels of sub-sonic projectiles. Suppressors are often incorrectly called
“silencers” since high-level sounds are still generated. Two recent studies have measured the
peak impulse levels in suppressed and unsuppressed conditions using both subsonic and
supersonic ammunitions measured at the left ear of the shooter.14, 72 Lobarinas et al. found that
suppressors (n=14) coupled to AR-15 rifles (n=15) reduced the mean peak levels by 18-22 dB
relative to the unsuppressed condition.14 Murphy et al. measured firearm noise with two different
rifles (.223 and .308 caliber) using subsonic and supersonic ammunition, with and without
suppressors, and at three different microphone locations (shooter’s right ear, left ear, and at the
instructor’s position 1 meter behind the shooter).72 Peak SPLs for the subsonic ammunition
ranged from 100 to 132 dB SPL in the suppressed conditions across microphone locations. The
levels were 127 to 149 dB SPL for the unsuppressed conditions. Peak SPLs for the supersonic
ammunition ranged from 120 to 137 dB in the suppressed conditions compared to 148 to 161 dB
for the unsuppressed conditions. It appears that combining the use of suppressors with subsonic
ammunition can further reduce the exposure, based on these preliminary studies on a limited
number of firearms and suppressor combinations. The peak reduction afforded by the use of a
suppressor does not always reduce the peak level below 120-140 dB, and marketing claims to the
contrary should be considered with skepticism, especially in the context of firearms with short

Prevention of NIHL from Recreational Firearms 25
barrel lengths or when supersonic ammunition is fired.14,72 The use of hearing protection may
still be warranted even when using a suppressor.
Hearing Protection Devices Designed for Use in Shooting Sports
Despite the recognition that firearms produce hazardous levels of sound that can damage
the auditory system, 38% of adult target shooters and 95% of adult hunters report never wearing
hearing protection devices (HPDs) while shooting, in the past year.45 The inconsistent pattern of
HPD use in youth recreational firearm users somewhat mimics the behavior of adults.42,73,74 The
majority (62%) of youth aged 10-17 years reported never wearing hearing protection while
hunting (16%, always) and 15% never wore HPD while target shooting (56%, always).6 The
increased use while target shooting is likely related to the enforcement of shooting range rules
and a lower reliance on the audibility of environmental sounds as compared to hunting sports.
Additionally, the majority of recreational shooters are unfamiliar with alternatives to
conventional hearing protectors that provide minimal attenuation for low-level sounds but
provide substantial protection for high-level impulses. It is encouraging to note that youth who
shoot are more likely to report using hearing protection regularly than their peers.50
The attenuation of hearing protectors is commonly labeled (and marketed) with values
obtained using continuous noise at hearing threshold levels in a laboratory setting (e.g., noise
reduction rating (NRR)). When products designed for impulse noise are tested under these
conditions the NRR is negligible (< 10 dB) and the consumer is left misinformed. In reality, the
attenuation of an impulse tends to increase with the level of the impulse for traditional earplugs
and earmuffs.75-77 From a simplified perspective, auditory protection is dependent upon the
proper fit of the HPD and sufficient attenuation for the peak sound pressure level of the impulse.

Prevention of NIHL from Recreational Firearms 26
Two types of hearing protectors have been developed to further address the need for
situational awareness while shooting; electronic hearing protectors and small-orifice, filtered or
valved passive protectors. Electronic HPDs rely upon a power supply and utilize circuitry to
restore audibility for the wearer when sounds are below approximately 85 dB SPL and limit the
long-term average output level to 82-85 dB SPL. Electronic devices may include the option of
amplification of low-level sounds, which may be highly advantageous for hearing-impaired sport
shooters and for hunters to hear approaching game. The passive attenuation characteristics of the
electronic protector (i.e., electronics turned off) determine the attenuation for high-level impulse
sounds greater than 150 dB SPL. The circuitry is actually too slow to respond, and the high-level
impulse signal is clipped when it is processed. For peak levels less than 130 dB SPL, electronic
circuitry performance may be a significant contributor to the impulse levels measured under the
protector, particularly in the case of devices designed to add gain or compress high-level
signals.77 Electronic hearing protectors come in a variety of styles, including: circumaural
earmuffs, universal-fit insert earplugs, custom-fit earplugs, and behind-the-ear devices connected
to an earplug. An electronic, level-dependent, in-the-ear style protector may preserve sound
localization in the horizontal plane better than an earmuff or behind-the-ear style electronic
protector.78,79
The second type of protector designed for high-level impulse attenuation utilizes a small-
orifice, filter or a mechanical valve. At low levels of sound pressure, audibility is maintained,
while at high levels the acoustic pressure flow through the orifice becomes more turbulent and
provides increased acoustic resistance.80 Flamme and Murphy caution that increased acoustic
resistance does not necessarily result in adequate protection, and the ear may be exposed to 150 -
165 dB peak SPLs even when protectors are properly fit.21 Berger and Hamery demonstrated that

Prevention of NIHL from Recreational Firearms 27
mechanically valved hearing protectors may only provide 10 dB of peak noise reduction through
peak SPLs of 170 dB, and of greater concern, amplified peaks below about 150 dB SPL.81
Ongoing work is underway to standardize laboratory testing and performance characteristics of
hearing protectors designed for auditory protection from impulse noise across a range of impulse
levels (ANSI S12.42).
Dual hearing protection (earplug worn in combination with an earmuff) provides the
greatest protection.82 Recreational shooters may find it advantageous to use a conventional
earplug with electronic earmuffs. The choice of hearing protection may also vary as a function of
shooting activity. It is much easier to comply with dual hearing protection use in a target-
shooting range environment than when bird hunting in a heavily wooded area where earmuffs
become entangled in brush. Regardless of the style of hearing protector, the fit of the protector is
critical. Eyeglass temples, hats/caps, hoods that interfere with the seal reduce mean attenuation
across test frequencies by 5-15 dB.82,83 It is also advisable to remind shooters that the HPD
should be securely in place before shooting, and that physical movement related to the force of
the recoil may “kick” the earmuff off the ear. Wearer comfort is also an important consideration
driving the choice of protector(s), in order to assure adequate wear time.
It is common for shooters to recognize the need to use HPDs when shooting larger
caliber/gauge firearms, and dismiss the need for protection when shooting smaller calibers, such
as a .22 pistol/rifle. This erroneous decision making arises from poor relative loudness judgments
being made across gunshots from different firearms. The high probability that a recreational
shooter has a hearing loss, combined with the brief signal duration of a gunshot, will often lead
the shooter to underestimate the sound level of the impulse and perceive it to be innocuous.
Reliance upon subjective judgments of auditory risk should be discouraged and hearing

Prevention of NIHL from Recreational Firearms 28
protection should be used for all types of recreational firearms. It may be useful to use an
analogy in which the comparative sound energy emitted by a single shot from a firearm at 140
dB peak SPL is equivalent to almost a full day exposure to continuous noise at 85 dBA integrated
with a 3 dB exchange rate. Firing 1000 rounds would then incur the equivalent of 3 years of
allowable noise exposure. In other words, the number of allowable shots add up quickly over a
lifetime of sport shooting. This may serve to put the risk in perspective for the shooter and help
them recognize the cumulative risk of multiple shots and stresses the importance of routine use
of hearing protection. Consistent use of hearing protection by adults is also an important aspect
of mentoring health and safety behaviors for young shooters.
EDUCATION
The diversity of firearm-related activities and recreational firearm users will necessitate
the creation of unique public health messaging and interventions designed, and evaluated for
specific audiences worldwide. Understanding the unique shooting and audibility demands of
each firearm-related sport will better inform training content. Health communication science is
useful as a framework for developing, implementing and evaluating hearing loss prevention
programs for firearm users. Dangerous Decibels® has adapted the small-group classroom
program to incorporate firearm-specific content in terms of acoustic trauma from a single shot,
sound levels of various firearms, types of specialized hearing protectors for shooting sports and
modeling peer-interactions at a shooting range.84
Partnerships are needed between the hearing health community and shooting sport and
wildlife conservation organizations to develop and disseminate accurate information and
promote organizational resources that support hearing loss prevention efforts. The shooting

Prevention of NIHL from Recreational Firearms 29
sportsperson depends on informed healthcare providers and evidence-based product information
to equip them to preserve their hearing and afford long-term opportunities to enjoy their sport(s)
safely. Aim to be an informed resource in your community.
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