What are vibrations that travel through gases, liquids, and solids and are processed by the hearing apparatus?

The correct answer is sound waves. Sound waves are mechanical vibrations that propagate through different media, including gases (like air), liquids (such as water), and solids (for example, metal). These vibrations occur when an object vibrates and creates pressure changes in the surrounding medium, which then travel outward from the source.

When these waves reach the human ear, they are processed by the auditory system, where the vibrations are converted into electrical signals that the brain interprets as sound. Sound waves encompass a wide range of frequencies and intensities, and they are the foundational concept in understanding how we perceive auditory experiences.

The other options do not accurately represent the fundamental nature of these vibrations. Echoes are reflections of sound waves off surfaces, noises refer to any sound but lack the structured frequency characteristics found in sound waves, and tones specify pitches within the context of sound but do not encompass the broader definition of how sound waves operate through different mediums.