So, for furtherance of one of the things that keeps me awake at night wondering about things (see below), I think that mitochondria would sound something like a washing machine filled with Jello and power tools on the wash part of the cycle. Maybe throw a hedgehog in there too to make it sound right.
The 3 membranes makes imagining their sound difficult.
The washing machine wash cycle "chug, chug, churn, churn, chug" would be more or less the continual flux of electrons through the electron transport chain. The Jello only makes sense because the mitochondria do, after all, contain cytosol-like stuff. The power tools for the shunting of materials and supplies across the membranes, including the spinning off of ATP (that'd be the buzzsaw). And the hedgehog to introduce a dimension of chaos (yo biology!) that would otherwise not be present.