Within a sound wave, the particle refers to a constituent of the medium through which the sound is propagating. The medium could be a gas (such as air), a liquid (such as water), or a solid (such as a metal).
In the case of sound traveling through a gas, like air, the particles are the individual molecules of the gas, such as nitrogen (N2), oxygen (O2), carbon dioxide (CO2), and others. These gas molecules are constantly in motion, colliding with each other and transferring energy in the process.
When a sound wave passes through the medium, it causes these molecules to vibrate. The vibrations create a pattern of compressions and rarefactions, where the molecules are pushed closer together (compression) and then spread apart (rarefaction). This pattern of molecular motion is what propagates as a sound wave.
It's important to note that within a sound wave, the particle is not a separate entity or a distinct "thing" apart from the medium. Rather, the particle refers to the individual components of the medium that participate in transmitting the sound energy. The particle's motion and interactions within the medium allow the sound wave to propagate through it.
In summary, within a sound wave, the particle refers to the individual molecules or particles of the medium (such as gas, liquid, or solid) that vibrate and transfer energy as the sound wave travels through it.