What is a sine wave?

• A. The simplest type of sound wave, containing only one frequency.
• B. The amplitude of a sound wave
• C. The timbre of a sound wave
• D. The duration

Answer: (A)

A sine wave is the purest possible type of sound wave: a smooth, regular oscillation that contains only one frequency. In mathematical terms, it follows a sine function, producing a single, constant cycle per second with a fixed amplitude and no extra frequency components (no harmonics). This is what we hear as a pure tone, which makes it ideal for isolating pitch in experiments because there’s nothing else in the spectrum to shape the sound.

Understanding the other terms helps connect these ideas: the amplitude is about how tall the wave peaks are, affecting loudness but not the wave’s basic shape. Timbre is the quality that lets you tell different sounds apart (like a piano versus a flute) and arises from having multiple frequencies and their relative strengths. Duration is simply how long the sound lasts. None of these describe a single-frequency, smooth waveform the way a sine wave does.