2.1. 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 to vibrate. As the microphone membrane vibrates, it changes the magnetic field of a magnet behind it. This varying magnetic field causes a very small electric current to flow from the microphone’s wires. That current is what we actually measure with this gadget.