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מצורף כאן מאמר המסביר את מבנה האוזן והסכנות מחשיפה למוזיקה בעוצמות חזקות, כפי שהרבה מהאמנים המופיעים נחשפים להן. כמו כן מוסבר כיצד להגן על האזנים מפני סכנות אלו. בסוף הכתבה הבאתי את טבלת משכי זמן מירביים לחשיפה לרעש בעוצמות שונות (והפעם, בעברית)
09:24 (17/09/17) Ariel Arielly

The Musician’s Guide to Hearing Protection — from a Doctor! By Todd Page, MD(*) on Sep 15, 2017M Why would a major touring act like AC/DC abruptly cancel 10 concerts on their Rock or Bust World Tour? In March 2016, lead singer Brian Johnson was advised by his physicians to “stop touring immediately or risk total hearing loss.” Though this was a dramatic and alarming announcement, it highlights what can happen if musicians don’t proactively protect their hearing. A quick search for “musician hearing damage” reveals an internet-fueled information avalanche out there, but we’re all busy musicians, right? Who has the time to try to decipher facts vs. old wives’ tales? Here’s a concise guide of what you need to know to protect your hearing. How do we hear? Elegant in design, the whole hearing process is fascinating to discuss, but here’s a brief overview. The ear translates the physical movement of air (pressure variations known as sound waves) into electrical data (called nerve impulses) that is transmitted to the brain to process and interpret what is going on in the world around us. Sound waves collected by the outer ear travel to the eardrum, which works like a microphone, taking sound waves and changing them into mechanical energy. Just past the eardrum, three tiny bones, called the ossicles (you may remember learning about the hammer, anvil, and stirrup back in biology class), augment that signal by a factor of 22 and vibrate the oval window, which is the interface between the middle ear and the inner ear. Movement of the oval window pushes (and pulls) inner ear fluid within the snail-shaped cochlea, creating shifts that activate hair cells along the organ of Corti; these cells are arranged sequentially by frequency response from high (nearest the oval window) to low (at the end of the ascending cochlear spiral). Triggered hair cells activate corresponding neurons that are stimulated proportionally to the intensity of the wave. This “data” is then instantly communicated to the brain, where it’s interpreted and presented to your consciousness as sound. What can go wrong? Being such a complex system, however, there are many opportunities for things to misfire. Problems can be broadly divided into short-term and long-term issues. More acute deficits can result from ear canal obstruction (infections like swimmer’s ear, retained water from swimming or bathing, or wax buildup) or “foreign bodies” (I’ve seen my share of interesting things in people’s ears — from cockroaches and spiders to food like peas and carrots!). The middle ear can be affected by infection or allergies, which produce a buildup of fluid and/or pressure that alters the frequencies reaching the cochlea. Longer-term hearing issues are typically less easy to correct. Some examples include eardrum damage (perforations from trauma or infection, chronic scarring from frequent ear infections over the years), ossicle wear (from arthritic changes or trauma), inner ear hair cell damage (usually from inappropriate sound exposure), medications, tumors, smoking, and even chronic medical conditions such as diabetes and hypertension. Neurons from the cochlea to the brain can be disrupted by stroke or head/brain trauma and affect hearing, as well. Moreover, there is inevitable age-related degeneration, called presbycusis, which typically begins in a person’s 50s, but may even start developing in the late teens to early 20s according to some studies. Presbycusis affects high-frequency sounds the most, at least initially, and affects about one in three people by age 65. As musicians, though, we must understand and respect the most preventable cause of long-term damage — repeated high-level sound exposure. Several factors contribute to this type of degradation, including volume (measured as sound pressure level in decibels, abbreviated dB SPL), frequency distribution, duration of exposure, individual susceptibility (genetics), and age. Defining what’s considered safe might surprise you! For reference, consider that baseline ambient noise in a quiet room runs around 40dB, a hair dryer around 90dB, a lawn mower around 110dB, and a rock concert in front of the speakers? That’s 120dB or more. The threshold of pain is around 140dB. Within this framework, the National Institute for Occupational Safety and Health (NIOSH) guidelines recommend exposure to 85dB (A-weighted) levels for no more than 8 hours a day. Every 3dB correlates to a doubling in power (volume doubling is typically reported as a 10dB increase, but in terms of the inner ear, we’re interested in the power-doubling factor of 3dB), which means that for every 3dB increase, the recommended “safe” listening interval halves. So at 88dB exposure, by the NIOSH recommendations, the limit is 4 hours. At the 110dB range (such as mowing your lawn) it’s 30 seconds. That 120dB rock concert? The limit is 7 seconds! That’s right — after 7 seconds, you risk permanent hearing damage. Ongoing exposure of the cochlea’s hair cells to these high SPLs causes physical wear and destruction, and ultimately they can no longer carry the sound movement to the nerve cells. Symptoms Fortunately, there are warning signs that indicate damage is occurring. Most of us have experienced that hollow or ringing sense that persists after enjoying a live concert that was just a bit too loud; that sensation is the chorus of stressed and dying hair cells. Although it usually goes away after several hours, inevitably there is some degree of permanent damage, and it’s an example of one of the earlier signs of hearing loss, called tinnitus. In one study, the incidence of noise-induced hearing loss among musicians was nearly four times the general population, and tinnitus was 57% more likely among musicians. [Check out this article on Incidence and Relative Risk of Hearing Disorders in Professional Musicians.] Coldplay’s lead singer, Chris Martin, has battled tinnitus for years. He said, “Looking after your ears is unfortunately something you don’t think about until there’s a problem. I’ve had tinnitus for about 10 years, and since I started protecting my ears it hasn’t got any worse…but I wish I’d thought about it earlier. Now we always use molded filter plugs, or in-ear monitors, to try and protect our ears. You CAN use industrial headphones, but that looks strange at a party.” Other well-known musicians who have shared their struggles with tinnitus include Phil Collins (who essentially retired because of it), Eric Clapton, Neil Young, Pete Townshend, Jeff Beck, Bono, and Sting, many of whom regret that they didn’t do more to protect their ears earlier in their careers. According to Lars Ulrich from Metallica: “If you get a scratch on your nose, in a week that’ll be gone. When you…damage your hearing, it doesn’t come back. Once your hearing is gone, it’s gone, and there’s no real remedy.” There is the natural assumption that this is a rock star-only problem, but classical and orchestral musicians are at equal (and in some studies, greater) risk. For example, violin players can develop asymmetric hearing loss because of the proximity of the left ear vs. the right to the instrument. Actor Steve Martin reported developing permanent tinnitus after a shootout scene in the movie Three Amigos. Tinnitus, however, is just one of many symptoms that goes with hearing loss. Early hearing loss can scramble speech clarity and recognition — especially in noisy or busy environments. You may find yourself frequently asking people to speak up or talk more slowly, and perhaps your favorite songs sound different than when you were younger. It could manifest itself in the studio environment by making your mixes sound odd. Sometimes a hypersensitivity to certain frequencies, called hyperacusis, can indicate hearing loss as well. While the ear does have some defense mechanisms to protect itself, even these can adversely affect how you hear sounds. In particular, Temporary Threshold Shift (TTS) is a phenomenon where prolonged exposure causes the hair cells and nerves to desensitize, or shift their frequency response. A classic example would be after leaving a loud concert and listening to the radio on the way home, you notice the next morning that the radio volume was set very loudly. Another defense mechanism is related to a tiny muscle anchored to the ossicles that reflexively contracts with sudden loud noises. This reaction decreases the amount of vibration passed along to the inner ear. While these autonomic protective measures help, they also impact what you hear. It is the root cause of the “listening fatigue” that happens when trying to mix and/or master a song for long periods of time, and it plays a role in fader creep that mix engineers know all too well. This underlies the recommendation that you take frequent breaks from mixing or mastering — not only do rest times help protect your hearing, but they also keep your body’s TTS defense mechanisms from messing with your mix! The ultimate motivation, though, should come from the fact that repeated trips into the TTS zone eventually lead to what is called a Permanent Threshold Shift (PTS), which irreversibly affects sound perception. Typically, PTS will affect the 4kHz frequency range (the upper midrange) and then expand into surrounding frequencies over time, with the length of exposure playing an important role. Affected hair cells and nerve fibers lose their threshold responses, and some even inappropriately increase response, which wreak havoc on the accurate sound discrimination that musicians depend on. Damage can be present even without perceptible symptoms — but a formal hearing test can reveal defects even before symptoms are noted. Many sound engineers get their hearing tested annually to discover defects before they become symptomatic, and likely irreversible. Unfortunately, once your hearing is damaged, there’s nothing science or medicine can do to get it back besides using some kind of hearing aid or noise-canceling device. While there are a few medications that can mitigate tinnitus symptomatically, there are none that reverse it or even allow the ear to heal. This irreparable damage is the main reason that we focus on protecting and preserving our hearing. Preventing hearing loss While the factors discussed above play a role in hearing loss, they affect us all differently. Some people may have constant loud sound exposure for years and suffer no ill effects, and others have long-term damage after just one event. Yet there is no debate that repeated exposure over time is destructive, and as such, every effort to mitigate this should be a priority for every musician. The good news is that even in the presence of damage, progression can be prevented by taking some immediate steps. The most important thing is to vigorously defend your ears! If you enjoy “feeling” the loud music at a rock concert, make sure you wear ear protection so you don’t ruin your hearing.Second, develop the habit of paying attention to the volume levels around you by using a dB meter. If you don’t have a dedicated device, such as the Galaxy Audio Check Mate CM-130 SPL Meter, you can easily use a smartphone app, many of which are free. Use quality speakers, headphones, or in-ear monitors to get accurate frequency response, but be careful to keep their volume levels in check at all times.Third, get in the habit of using earbuds or plugs when you’re in any loud environment (not just music venues). Put them in when using power tools, shooting firearms, mowing the grass, or going to that monster truck rally or sporting event.Fourth, when you do use in-ear protection, use best practices. Be sure they seal well in your ear canals — not only for comfort, but because a leaky seal defeats the purpose of using them in the first place. Never leave one in-ear monitor (IEM) out and one in; that’s a sure-fire way to damage your hearing over time. For musicians onstage, if you are having trouble hearing what’s going on around you (which actually means you’ve got a good seal), consider adding an ambient mic channel to your in-ear mix or perhaps getting a newer IEM model that has a port to allow external sounds to enter as well, such as Westone’s Am Pros. Start protecting your ears now! The first and easiest step to protect your hearing is to get a cheap pair of foam earplugs. They cost a few bucks and can be found in most hardware stores. The advantage is that they are inexpensive and do reduce the volume at your ear, but non-musician earplugs usually reduce higher frequencies and subsequently produce a muffled or muddied sound. Musicians’ plugs reduce all frequencies equally and thus preserve the musical soundscape in its entirety, though at a safer volume. They can be made of softer silicone, or some are a more rigid material that will soften in the ear canal from your body heat to allow a stable seal. Hearos Rock ‘n Roll Earplugs offer a good fit and are washable. Better still are high-fidelity earplugs like the Etymotic Research ETY-Plugs, which maintain the natural frequency response while minimizing noise exposure. Also, Westone makes a set for just under $50 that comes in 16dB and 25dB attenuation levels. Better hearing protection can be achieved using active attenuating earbuds. The sound attenuation is digitally controlled and allows a variable level of adjustment, but that comes with a price, costing several thousand dollars. To see the full range of hearing protection that Sweetwater carries, check out our Earplug page. Selecting in-ear monitors In-ear monitors are great not only for musicians, but also for casual listeners. They typically offer a better fit and greater sound isolation, and they sound better than generic earbuds. If you’re shopping for in-ear monitors, there are many factors to consider, but in terms of hearing protection, consider how much isolation they provide and decide whether you want universally fitting IEMs or custom-molded monitors. Either way, having IEMs with interchangeable ambient filters is a great option, because you can either have more complete isolation using them as earplugs or put in a passive filter that will attenuate volumes less dramatically depending on the application. Pro Tip: For musicians who want more information about selecting in-ear monitors and using them wirelessly, check out our “Wireless In-ear Monitor Primer.” The point of this discussion is to help you appreciate that you’re only born with one set of ears. It’s never too early (or too late!) to learn to take care of them. Now that you understand how your ears work, how they can be damaged, and the symptoms of damage and how to prevent it, you can take steps right away to protect them! If you’re not doing anything at all at this point, a simple first step would be to get a basic set of foam earplugs to wear to concerts at a minimum. In this increasingly noisy world we live in, we’d suggest keeping earplugs with you all the time. Just toss a set of foam plugs in your backpack, purse, or briefcase. (*)About Todd Page, MD Todd Page, MD, is Sweetwater’s in-house family doctor and provides medical care for our employees and their families. Not only is he passionate about medicine, but he's also an avid musician and photographer with a bachelor’s degree in music (trumpet and piano) from the University of Colorado. Todd toured for five seasons with the New Light Singers and Orchestra and subsequently graduated with honors from Indiana University School of Medicine in 1996. He loves his responsibilities at Sweetwater and also plays bass and sings with his church’s worship team and a local trio, helps lead the church’s tech team, works on audio and video projects out of his home studio, and rarely sits still. Read more articles by Todd » מן חשיפה מותר לרעש חזק, יורד ככל שעולה עוצמת הרעש. עוצמת הרעש ב-dB זמן מותר לחשיפה 90 8 שעות 95 4 שעות 97 3 שעות 100 2 שעות 102 90 דקות 110 20 דקות 115 15 דקות על פי הוראות קרפ"ר, משך הזמן המותר לאדם להיות חשוף לעוצמה של 85 דציבל הוא 8 שעות ביממה. יש להדגיש כי חשיפה לעוצמות רעש העולות על 115 ד"ב, תגרום לנזק מיידי לשמיעה, נזק שאינו הפיך!!!

 
 
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