ARTICLE BY ANDY SAUNDERS The body reacts to noise as a danger signal. Our nervous systems haven't had time to evolve from the time when the loudest noise you'd hear would be a mammoth charging at you. When we're exposed to loud noise, blood pressure rises, heart rate and breathing speed up, muscles tense, perspiration increases and hormones are released into the bloodstream. It's in your best interest to keep the noise in your life to a minimum. Everyone has felt ringing in their ears after a loud concert or a party; continued abuse of your ears makes that ringing (called tinnitus) permanent. Although loud noise can damage your ears (usually irreparably), it affects the heart most. Blood vessels constrict, pressure rises and cholesterol and triglycerides also rise. The increased hormonal activity steps up the secretion of acid in the stomach, possibly causing ulcers. Loud sounds also affect the reproductive system in a manner similar to alcohol: increasing sexual drive while decreasing potency. In addition, loud sounds affect the level of white blood cells and gamma globulin in the bloodstream, lowering the efficiency of the immune system. Sound is measured two ways: by level and by the frequencies that make up that level. The adolescent human ear can hear sound waves at levels between a low 20 cycles per second, or 20 hertz (Hz), and a high of 20,000 cycles per second, or 20 kilohertz (kHz). Low frequencies are a dull rumble, high frequencies a shrill whine. As we get older, frequency response drops. A middle-aged person may not hear beyond 10,000 Hz (10 kHz). The human ear is most sensitive to sounds in the 1 to 4 kHz range, the usual frequencies of human speech, and damage occurs first in these areas. Hearing loss is a gradual process, unnoticed by the loser. Noise doesn't have to hurt your ears to hurt your hearing: the Occupational Safety and Health Administration advises that habitual exposures to 85 dB for more than eight hours cause hearing loss. If you are regularly exposed to noise at the 95-dB level (10 times as loud), one hour is about the limit. Above 105 dB, your hearing can be damaged by repeated 15-minute journeys. Motorcyclists risk hearing loss. Noise is the constant companion of a motorcyclist, no matter how quiet the bike. Pushing any projectile through the air at speed creates turbulence and noise, whether that projectile is a rifle bullet, an airplane or a human head. Riding with a bucket on your head creates more turbulence at the mouth of the bucket, and more noise. Some (though very few) full-face helmets can be noisier than no helmet at all. Even the best helmets can't close out all the wind noise, so if you ride long distances frequently, you need to wear ear protection. The most convenient, the foam earplugs of the E.A.R. type, cut sound-pressure levels by 30 dB or so when properly inserted, and nearly every California motojournalist uses them. Unfortunately, they are all breaking the law. California's vehicle code states: "No person operating a motor vehicle or bicycle shall wear any headset covering, or earplugs, in both ears. The prohibition does not apply to any person wearing hearing protectors in the form of custom earplugs or molds that are designed in a manner so as to not inhibit the wearer's ability to hear a siren or horn from an emergency vehicle or a horn from another motor vehicle." Of course, you can buy custom earplugs, but they are uncomfortable inside a well-fitting full-face helmet and expensive at around $100 a set. Avoiding damage to your brain is more important than avoiding damage to your hearing, but by selecting the right helmet, you can do both. The results are interesting. The quietest helmet at 60 mph is much quieter than the loudest at 30, and the loudest helmet has the potential to damage hearing after quite a short exposure. At 30 mph, the padding of the open-face Bell was springy enough to effectively insulate the ears. At 60, the padding had deflected enough to make it one of the noisiest helmets. Due to the dfflerence between the human ear and electronic microphones, we expected the noise-test results to disagree with tester's subjective evaluation but we were pleasantly surprised. With a couple of notable exceptions, what we heard is what the machine got. The exceptions: The Kiwi K22 seems quieter than it is, the Sure louder. The Kiwi seems quieter because all its noise is low in frequency, and even at 60 mph the frequency level doesn't intrude much into the speech band of 1 to 4 kHz. The Sure has exactly the same dB level at 60 mph, and in fact is quieter at 30 than the Kiwi, but it seems louder and more unpleasant because a significant component of its noise occurs in the speech band. We expected that our favorite, high-priced helmets would do well on this test, and we were right. As a nule, the higher the price, the better padding and noise protection. The exceptions were AGV's Phantom and Thema, where price seems directly proportional to noise level. (But these helmets are also light, with large eye ports.) Shoei's X8, touted as the quietest, most aerodynamic helmet on the market, is quiet because it has more sound-deadening padding in the comfort liner and is sized to fit very tightly. Our tester, who is on the borderline between large and extra large in Shoei sizes, found he was more comfortable in a large-model RF200 than an extra-large X8; the RF200 was quieter too. Would riding without a helmet do more damage to your hearing? Yes. Research shows that almost any open or full-face helmet attenuate enough sound to afford some hearing protection. Shorty helmets are a real hearing risk, and motorcycle policemen may suffer significant hearing loss after years of wearing one (which should give cops who want better helmets a strong case). A helmet that has less sound insulation will not necessarily allow you to hear more at highway speeds. For a specific sound to be audible, the signal-to-noise ratio would theoretically have to be greater than 1-to-1. In other words, if you are experiencing a 110-dB roar in your helmet, any siren or horn will have to be louder than 110 dB for you to hear it (in practice, sirens operate at high frequencies, so you may hear one even when the signal-to-noise ratio is less than 1-to-1). Earplugs effectively dampen wind noise, yet allow shrill sirens to be heard clearly. However, if you drive in very slow traffic most of the time, where you need to notice external environmental sounds, a quiet helmet with thick padding may mask some of these essential sounds. These tests were perforrned without engine or external traffic noise, so they represent the minimum noise present at those speeds. Engine noise and external traffic noise add to the racket inside your helmet, though you'll notice it more at 30 mph than at 60 mph. Helmets like the Sure S8-N, AGV Sukhoi, Bieffe B3R, CTS, Fulmer, Hondaline, MDS, Nolan N35 and Jeb's all sounded louder than their rankings would suggest. None of these are fiberglass lids, suggesting that the type of material used in construction may play a part or that the cost of materials has an effect. Certainly, the fit between face shield and shell was important. The wind whistled through the gaps in the Sure's shield, adding to the cacophony. The plastic helmets were also at a relative disadvantage due to their single shell size. Helmets sized large or extra large were used exclusively for this test, and the polycarbonate lids have only one size shell for all head sizes. Thus, extra-small wearers get much more EPS and comfort linerŅ and more sound attenuation. How much are you at risk? If you wear a well-fitting, quiet helmet on short journeys to work every day, you'll probably never need ear protection. But motorcyclists who ride often or far; couriers, policemen, motojournalists and high-mileage touring riders do need protection. You may find that a helmet-closure device, like Noj's chin shield or Lockhart's Apple Warmer, will cut down the level of sound reaching your ears, although the face shield will fog up more easily and you'll experience more heat in warm weather. A future generation of helmets is likely to offer active noise-reduction (ANR) technology, currently in use in airplane headsets. ANR works by generating mirror-image sound waves, waves of opposite phase, for every component of the environment's noise. The two sound waves cancel each other out. Since even the best current ANR system takes a few seconds to precisely analyze and duplicate the sound-wave components of noise, ANR will work best on touring machines, where noise remains constant. Sport-bike owners, don't throw away your earplugs.