The inability to hear sound from an infinite distance away is due to several factors related to the nature of sound waves and their propagation.
Sound Attenuation: Sound waves gradually lose energy as they travel through a medium. This phenomenon is known as attenuation. The further sound waves propagate, the more they spread out and become weaker. Eventually, the sound intensity becomes so low that it falls below the threshold of human hearing. Therefore, at a certain distance, the sound waves become too faint to be perceived by our ears.
Inverse Square Law: Sound obeys the inverse square law, which states that the intensity of sound decreases inversely with the square of the distance from the source. In simpler terms, when you double the distance from the sound source, the sound intensity diminishes to one-fourth of its original level. This relationship highlights how quickly sound energy dissipates as distance increases.
Ambient Noise: In the environment, various sources contribute to ambient noise, such as other sounds, natural phenomena, or technological activities. As you move away from the sound source, ambient noise becomes more prominent relative to the diminishing sound intensity. At some point, the ambient noise levels can mask or override the sound you are trying to perceive.
Absorption and Reflection: Sound waves can be absorbed or reflected by objects in the environment. As sound travels over a distance, it encounters different materials and surfaces that can absorb or reflect the sound waves. This can further contribute to the loss of sound energy and reduce its audibility at greater distances.
Considering these factors, it becomes clear that sound waves cannot propagate indefinitely and still be heard. They lose energy, spread out, and are affected by the environment, ultimately becoming too weak or overshadowed by other sounds. Consequently, sound becomes inaudible at extremely long distances, leading to the inability to hear it from an infinite distance away.