Which phenomenon leads to the sensation of sound being formed?

The sensation of sound is primarily formed through the vibration of sound sources. When an object vibrates, it generates sound waves in the surrounding medium, typically air. These vibrations create fluctuations in air pressure, which propagate as sound waves to our ears. Once these waves reach the auditory system, they stimulate the structures of the inner ear, leading to the perception of sound.

Understanding this phenomenon is crucial in the context of sound production and hearing, as it highlights the importance of the original sound source in the process of sound creation. Without the initial vibrations, there would be no sound waves to transmit or perceive. This underlines why the vibration of sound sources is the key element in sound formation, making it the correct answer in the context of the question. The other options, while related to how sound interacts with the environment, do not directly account for the creation of sound sensations as effectively as the vibrations of the sound sources do.