TED日本語 - マティアス・バスナー: 騒音が健康に有害な理由 ― そして私たちにできること

Do you hear that? Do you know what that is? Silence. The sound of silence. Simon and Garfunkel wrote a song about it. But silence is a pretty rare commodity these days, and we're all paying a price for it in terms of our health -- a surprisingly big price, as it turns out. Luckily, there are things we can do right now, both individually and as a society, to better protect our health and give us more of the benefits of the sounds of silence.

I assume that most of you know that too much noise is bad for your hearing. Whenever you leave a concert or a bar and you have that ringing in your ears, you can be certain that you have done some damage to your hearing, likely permanent. And that's very important. However, noise affects our health in many different ways beyond hearing. They're less well-known, but they're just as dangerous as the auditory effects.

So what do we mean when we talk about noise? Well, noise is defined as unwanted sound, and as such, both has a physical component, the sound, and a psychological component, the circumstances that make the sound unwanted. A very good example is a rock concert. A person attending the rock concert, being exposed to 100 decibels, does not think of the music as noise. This person likes the band, and even paid a hundred dollars for the ticket, so no matter how loud the music, this person doesn't think of it as noise. In contrast, think of a person living three blocks away from the concert hall. That person is trying to read a book, but can not concentrate because of the music. And although the sound pressure levels are much lower in this situation, this person still thinks of the music as noise, and it may trigger reactions that can, in the long run, have health consequences.

So why are quiet spaces so important? Because noise affects our health in so many ways beyond hearing. However, it's becoming increasingly difficult to find quiet spaces in times of constantly increasing traffic, growing urbanization, construction sites, air-conditioning units, leaf blowers, lawnmowers, outdoor concerts and bars, personal music players, and your neighbors partying until 3am. Whew!

In 2011, the World Health Organization estimated that 1.6 million healthy life years are lost every year due to exposure to environmental noise in the Western European member states alone. One important effect of noise is that it disturbs communication. You may have to raise your voice to be understood. In extreme cases, you may even have to pause the conversation. It's also more likely to be misunderstood in a noisy environment. These are all likely reasons why studies have found that children who attend schools in noisy areas are more likely to lag behind their peers in academic performance.

Another very important health effect of noise is the increased risk for cardiovascular disease in those who are exposed to relevant noise levels for prolonged periods of time. Noise is stress, especially if we have little or no control over it. Our body excretes stress hormones like adrenaline and cortisol that lead to changes in the composition of our blood and in the structure of our blood vessels, which have been shown to be stiffer after a single night of noise exposure. Epidemiological studies show associations between the noise exposure and an increased risk for high blood pressure, heart attacks and stroke, and although the overall risk increases are relatively small, this still constitutes a major public health problem because noise is so ubiquitous, and so many people are exposed to relevant noise levels. A recent study found that US society could save 3.9 billion dollars each year by lowering environmental noise exposure by five decibels, just by saving costs for treating cardiovascular disease. There are other diseases like cancer, diabetes and obesity that have been linked to noise exposure, but we do not have enough evidence yet to, in fact, conclude that these diseases are caused by the noise.

Yet another important effect of noise is sleep disturbance. Sleep is a very active mechanism that recuperates us and prepares us for the next wake period. A quiet bedroom is a cornerstone of what sleep researchers call "a good sleep hygiene." And our auditory system has a watchman function. It's constantly monitoring our environment for threats, even while we're sleeping. So noise in the bedroom can cause a delay in the time it takes us to fall asleep, it can wake us up during the night, and it can prevent our blood pressure from going down during the night. We have the hypothesis that if these noise-induced sleep disturbances continue for months and years, then an increased risk for cardiovascular disease is likely the consequence. However, we are often not aware of these noise-induced sleep disturbances, because we are unconscious while we're sleeping. In the past, we've done studies on the effects of traffic noise on sleep, and research subjects would often wake up in the morning and say, "Ah, I had a wonderful night, I fell asleep right away, never really woke up." When we would go back to the physiological signals we had recorded during the night, we would often see numerous awakenings and a severely fragmented sleep structure. These awakenings were too brief for the subjects to regain consciousness and to remember them during the next morning, but they may nevertheless have a profound impact on how restful our sleep is.

So when is loud too loud? A good sign of too loud is once you start changing your behavior. You may have to raise your voice to be understood, or you increase the volume of your TV. You're avoiding outside areas, or you're closing your window. You're moving your bedroom to the basement of the house, or you even have sound insulation installed. Many people will move away to less noisy areas, but obviously not everybody can afford that.

So what can we do right now to improve our sound environment and to better protect our health? Well, first of all, if something's too loud, speak up. For example, many owners of movie theaters seem to think that only people hard of hearing are still going to the movies. If you complain about the noise and nothing happens, demand a refund and leave. That's the language that managers typically do understand. Also, talk to your children about the health effects of noise and that listening to loud music today will have consequences when they're older. You can also move your bedroom to the quiet side of the house, where your own building shields you from road traffic noise. If you're looking to rent or buy a new place, make low noise a priority. Visit the property during different times of the day and talk to the neighbors about noise. You can wear noise-canceling headphones when you're traveling or if your office has high background noise levels. In general, seek out quiet spaces, especially on the weekend or when you're on vacation. Allow your system to wind down.

I, very appropriately for this talk, attended a noise conference in Japan four years ago. When I returned to the United States and entered the airport, a wall of sound hit me. This tells you that we don't realize anymore the constant degree of noise pollution we're exposed to and how much we could profit from more quiet spaces.

What else can we do about noise? Well, very much like a carbon footprint, we all have a noise footprint, and there are things we can do to make that noise footprint smaller. For example, don't start mowing your lawn at 7am on a Saturday morning. Your neighbors will thank you. Or use a rake instead of a leaf blower. In general, noise reduction at the source makes the most sense, so whenever you're looking to buy a new car, air-conditioning unit, blender, you name it, make low noise a priority. Many manufacturers will list the noise levels their devices generate, and some even advertise with them. Use that information.

Many people think that stronger noise regulation and enforcement are good ideas, even obvious solutions, perhaps, but it's not as easy as you may think, because many of the activities that generate noise also generate revenue. Think about an airport and all the business that is associated with it. Our research tells politicians at what noise level they can expect a certain health effect, and that helps inform better noise policy.

Robert Koch supposedly once said, "One day, mankind will fight noise as relentlessly as cholera and the pest." I think we're there, and I hope that we will win this fight, and when we do, we can all have a nice, quiet celebration.

(Laughter)

Thank you.

(Applause)