To perform _____ upon an audio signal is to reduce its amplitude, or strength.

The correct choice, attenuation, specifically refers to the process of reducing the amplitude or strength of an audio signal. In audio engineering and signal processing, attenuation is essential for controlling levels within a mix or when preparing signals for further processing or output. This process enables the sound engineer to customize the audio signal's volume to prevent distortion when signals are too strong or to ensure a balanced mix of different sound sources.

Other processes like distortion, amplification, and equalization serve different purposes. Distortion intentionally alters the audio signal to create a specific sound effect, often adding harmonic or inharmonic characteristics. Amplification increases the signal's strength, which is the opposite of attenuation, making the audio louder. Equalization adjusts the balance of different frequency components within an audio signal but does not inherently change the overall amplitude like attenuation does. Understanding these distinctions helps in effectively manipulating audio signals for desired outcomes in various applications.