Here's why:

* Amplitude refers to the maximum displacement of particles in a medium from their resting position as the sound wave passes through.

* Larger amplitude means the particles are vibrating with greater intensity, resulting in a louder sound.

* Smaller amplitude means the particles are vibrating with less intensity, resulting in a softer sound.

Think of it like this: imagine a string on a guitar. If you pluck it gently, the string vibrates with a small amplitude, producing a soft sound. If you pluck it harder, the string vibrates with a larger amplitude, producing a louder sound.