Sound particles are not molecules in the physical or chemical sense; they do not have defined physical or chemical properties or the temperature-dependent kinetic behavior of ordinary molecules. Sound particles are, then, indefinitely small (small compared to the wavelength of sound) so that their movement truly represents the movement of the medium in their locality.
Sound particles are not physical or chemical entities; they lack defined properties like molecules do, and don't behave according to temperature-dependent kinetic rules. Their small size (smaller than the wavelength of sound) allows them to accurately represent the movement of the medium around them.