Sound is not a state of matter like solids, liquids, or gases. Rather, it is a form of energy that travels through different states of matter, primarily through gases, liquids, and solids.
To understand this better, consider how sound is created. When an object vibrates, it causes the surrounding medium (which can be air, water, or solid material) to vibrate as well. These vibrations create compressions and rarefactions in the medium, leading to sound waves that propagate through the material.
In air, sound travels as a series of pressure waves, moving through the gas particles. In water, sound waves can travel even faster, and in solids, they can travel the fastest due to closer particle arrangement. Thus, while sound itself is not a state of matter, it requires a medium that can be in solid, liquid, or gas form to be transmitted.