For testing audio, square waves are typically used because they can reveal a lot about the system’s response with just a quick visual analysis. What’s so special about square waves? Why not use a typical “Sine Wave” or “Triangular Wave” for testing instead?
The reason is (if you remember your calculus class), the “ideal” Square Waves are composed of an infinite summation of sine waves of different frequencies. It has a single sine wave fundamental frequency, and all it’s odd harmonics. The amplitude of each odd harmonic is 1/n. Represented by this equation: (credits: Wikipedia)
