What is the difference between heat waves and sound waves?
Heat waves are a form of electromagnetic radiation. Therefore, they are transverse waves (oscillate perpendicularly to the direction of propagation) and need no medium to travel through. Sound waves, on the other hand, are mechanical waves, meaning they need a medium to travel through. If that medium is a liquid or a gas, sound waves oscillate longitudinally (in the direction they're traveling). If that medium is a solid, they oscillate both longitudinally and transversely.