When an object gives off sound the energy of the air (decreases, increases, or stays the same)

Increases.

Explanation:

Hello!

In this case, when objects give off, we can realize that the solid molecules undergo a phase transition to vapor; such is the case of volatile solids such as naphthalene, benzoic acid and those types of organic molecules.

In such way, since the air is now composed by a vapor and the air itself, if such process is able to give off sound as well, we are going to notice the energy of air increases because such waves are able to excite both air and the vapor molecules, even the solid is not given off as a vapor but as sound only.

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this could be newton#'s law of cooling. the cooling curve is exponential