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Environmental Monitoring with Arduino by Patrick Di Justo, Emily Gertz

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Chapter 2. Project: Noise Monitor/LED Bar Output

We cannot smell, taste, or touch a sound. But noise (which is what most of us call a sound we don’t like) is one of the most pervasive environmental contaminants around.

Noise pollution is defined as a sound that is constant, very loud, unwanted, or disturbing to everyday activities in the places we live, play, work, or learn. Cars on the street, planes overhead, construction equipment, or your neighbor’s loud TV leaking through the wall—these and more can become noise pollution. And it’s not merely a case of acute annoyance: According to the U.S. Environmental Protection Agency, noise pollution is directly linked to stress and stress-related illnesses (“all that noise is making me sick”), high blood pressure, fatigue, and hearing loss, among many other adverse effects.

Even the thick-skinned residents of New York City lose their cool when it comes to noxious sounds: unwanted noise is far and away the number-one complaint to the city’s 311 info and services line.

Measuring Noise: The Microphone

Sound is made by the movement of air molecules. When an object vibrates, it moves back and forth, creating pressure waves that compress the air first in one direction, and then in the other. These waves of compression travel outward in all directions from the source of the vibration until they hit an obstacle and get absorbed, reflected, or attenuated into nothingness.

When the wave reaches our microphone, its pressure causes a membrane in our microphone ...

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