Why can sound waves be used to determine the temperature of a medium (such as water) more directly than light waves?

So far from a show called Brain games, they did an exprimen that has relation to your question. They had you close your eyes, and they poured in cold water and hot water for both. When they did both the hot water and cold water, (separately of course) you could tell the difference. The cold water had some what of a higher pitched sound, and the sound of the hot water was deeper.