Final answer:
The correct answer is option A) sound amplitude.
Step-by-step explanation:
Decibels measure the loudness of sound, which is a reflection of sound wave amplitude. Specifically, decibels (dB) represent the intensity level of sound in a logarithmic scale. A sound's volume increases with greater wave amplitude, and normal human speech is typically around 60 dB. The term decibel itself is derived from the 'deci'- meaning 'ten', indicating that the number of decibels is ten times the logarithm to base 10 of the ratio of two sound intensities.
Unlike decibels, pitch is related to the frequency of the sound wave, while timbre refers to the quality or color of sound that distinguishes different types of sound sources, and is affected by the sound wave's shape that arises from reflections, resonances, and superposition. The name 'decibel' emphasizes that it is a relative and logarithmic measure to express the intensity level of sounds.