The of a sound wave measures the sound's loudness, while the of a sound wave measures the sound's pitch.

In the context of sound waves, the quality of sound is described using two key parameters: amplitude and frequency.

1. Amplitude: This measures the loudness of a sound. A sound wave with a greater amplitude will produce a louder sound, as it represents the maximum displacement of air particles in the wave. In simple terms, the louder the sound, the larger the amplitude of the wave.

2. Frequency: This measures the pitch of a sound. Frequency refers to the number of waves that pass a given point in a certain amount of time, typically expressed in hertz (Hz). Higher frequency sound waves result in higher pitch sounds, while lower frequency waves produce lower pitch sounds.

Therefore, the completed statement can be: "The amplitude of a sound wave measures the sound's loudness, while the frequency of a sound wave measures the sound's pitch."