What term describes the phenomenon of sound waves curving away from the earth?

The correct term for the phenomenon of sound waves curving away from the earth is refraction. Refraction occurs when sound waves travel through different layers of the atmosphere that have varying temperatures and densities, causing the waves to bend. This bending can be influenced by factors such as temperature gradients in the air, which can lead to sound waves being directed upwards instead of following a straight path along the surface.

While sub-refraction and super-refraction also involve sound propagation, they describe specific conditions in which sound can refract differently than standard expectations. Sub-refraction occurs when the sound waves bend less sharply than they would normally, potentially leading to diminished range. Super-refraction occurs when sound waves bend more sharply than typical due to a strong temperature inversion, allowing them to travel further along the ground. Both terms are related to variations in how sound travels but do not specifically identify the general phenomenon of sound curving away from the earth.

Thus, the overarching term for the bending behavior in the context given is refraction, which encompasses various conditions influenced by atmospheric factors.