Final answer:
The section of a sound wave with molecules spread apart, known as a rarefaction, indicates an area of less density, while compressions are areas of higher density. Sound can feel louder in denser regions and quieter in less dense areas. Amplitude also affects loudness but decreases over distance due to energy dispersion.
Step-by-step explanation:
The region of a sound wave where the molecules are spread out represents an area where the medium becomes less dense. This area is known as a rarefaction. In contrast, compression is the area in a sound wave where particles are pushed together, creating a region of higher density. As sound waves propagate, they alternate between compressions and rarefactions. The sound commonly feels louder where the medium is more compressed and dense, as sound energy is more concentrated in these regions.
The amplitude of a sound wave represents the energy of the wave, with greater amplitude indicating a louder sound. However, as sound travels, its amplitude decreases because the energy is distributed over a wider area, absorbed by objects, or transformed into thermal energy. In summary, rarefactions correspond to reduced density, compressions correspond to increased density, and the perception of sound's loudness is associated with these changes in density, as well as the amplitude of the sound wave.