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 assumed 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, with 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 cannot 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 the spaces,

in a time with 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
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,

and 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 association
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 cornestone
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.