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       #Post#: 21--------------------------------------------------
       The price of shooting
   DIR By: allmanav
       Date: September 15, 2017, 10:57 am
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       NIH Study: Supported by grants from the National Institutes of
       Health, David M. Nondahl and colleagues conducted a 1999 study
       on recreational firearm use and hearing loss. As one of the most
       focused research projects on this topic, 3,753 participants in
       Beaver Dam, WI, aged 48 to 92 years, responded to interviews and
       participated in hearing exams to assess the relation between
       recreational firearm use and hearing loss in a population of
       older adults.
       dB levels of common sounds
       Sound is measured in frequencies and decibels. Frequency
       indicates the pitch of a sound; decibels (dB) measure the
       loudness. Ten dB is barely audible; normal conversation occurs
       between 40 to 60 dB; a jet engine roars at 130 dB from 100 feet
       away. Sounds that are 120 dB or more can damage hearing and
       cause pain.
       After adjusting for age and other factors, high frequency (4, 6
       and 8 kHz) hearing thresholds tended to worsen as years of
       shooting exposure increased. This was true for both target
       shooters and hunters. The risk of having a marked high-frequency
       hearing loss increased 7 percent for every five years the men
       had hunted. Thirty-eight percent of the target shooters and 95
       percent of the hunters reported never wearing hearing protection
       while shooting in the past year.
       Dr. Thelen Interview: The website 4hearingloss.com published a
       2006 interview with Dr. Michael Thelen (Doctor of Audiology)
       titled: Gunshots—Hearing’s not-so-silent enemy.
       [Extract] “To understand hearing loss, we first must understand
       the dynamics of hearing. Noises result in airborne sound waves
       that create pressure as they enter the ear,” Thelen explained.
       “The eardrum and ossicles (tiny bones called the hammer, anvil
       and stirrup) turn this pressure into mechanical energy, which in
       turn creates hydraulic energy in the fluid of the cochlea, a
       snail-shaped organ in the inner ear. Rows of hair cells are then
       stimulated and the vibrating hairs create sensorineural signals
       that transfer sounds to the brain via the auditory nerve.
       Continued exposure to loud noises damages the rows of
       microscopic hair cells. Once we lose hair cells, hearing is
       lost.
       “As we gradually lose our hearing, we don’t notice it because we
       still hear the sound of a human voice, for example. Vowels are
       generally spoken as low-frequency sounds (for example, the ‘aw’
       sound in thaw) and can be spoken louder, but the consonant
       sounds (like the ‘th’ in thaw) are high frequency sounds that
       can’t be spoken louder. Thus a person with a high frequency
       hearing loss can’t tell the difference between thaw, raw and
       law. This is why many people who begin to lose their hearing
       believe other people are simply mumbling,” Thelen said.
       “Preventing hearing loss is easy and convenient for target
       shooters. Those who shoot trap, for example, wear earmuffs or
       earplugs while shooting. But hunting calls for specialized
       devices that allow normal sounds to be heard while clipping or
       otherwise dampening the high-decibel sounds of gunfire. The
       Walker’s Game Ear muffs, for example, can be adjusted
       electronically to allow normal sounds to enter and can even be
       set to amplify the sounds of approaching game. When a loud noise
       such as a gunshot enters the speakers outside the muffs, it is
       temporarily silenced with the electronic clip.”
       “In-the-ear plugs that mold to the outer contours of the ear
       generally do not seal as well as rollup-style plugs that fit
       tightly in the ear canal, or as well as muff-style protection.
       Ear plugs with a mechanical valve or filter that are supposed to
       allow normal sounds to pass while filtering loud noises
       generally are ineffective.”
       Finnish suppressor study
       These are the results measured by Dr. Rauno Pääkkönen during the
       Finnish Suppressor Project with an FN FAL .308 rifle both as
       unsuppressed (red line) and equipped with a T8L1 Scout Reflex
       suppressor (black line).
       Finnish Study: A 1992 study in Finland tested the use of firearm
       suppressors to assess the adverse effects of shooting ranges on
       nearby settled areas and to investigate possible solutions for
       hearing injuries among army officers, sport shooters and
       hunters. The chart above depicts the reduction of noise from a
       .308 cal. rifle with and without the use of a suppressor. The
       complete study can be found at guns.connect.fi/rs/measure.html.
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