Sound is the sensation we perceive when vibrations in the air are detected by our ears. Our ears convert these vibrations into electrical impulses that are transmitted to our brain. The brain distinguishes three main characteristics of sound: pitch, timbre, and amplitude. Pitch is determined by frequency and is measured in Hertz. Timbre refers to the unique tone quality of a sound and is determined by its frequency content. Amplitude describes the loudness or volume of a sound and is measured in decibels. Synthesizers allow users to manipulate these three characteristics to create and shape unique sounds.