Final answer:
The decibels of a sound wave decrease when the amplitude of the sound wave decreases, reflecting the direct relationship between the amplitude of a sound wave and its decibel level.
Step-by-step explanation:
When the amplitude of a sound wave decreases, the decibels of a sound wave decreases. This is because the decibel level of a sound is directly related to the amplitude of the sound wave—as amplitude goes up, the decibel level increases, and as amplitude goes down, the decibel level decreases. This relationship is illustrated by the fact that a change in sound intensity level by about 3 decibels corresponds to a doubling or halving of the sound's intensity, thus a decrease in amplitude, which relates to sound intensity, would result in a decrease in decibels. Factors such as distance can affect the amplitude as it can spread the energy over a larger area, leading to a decrease in amplitude with increased distance from the sound source.