Yes, the sound travels at the speed of sound; it does not travel at the speed of light.
But, the sound we are talking about is the sound between the mouth and the mike, and between the ear piece and the ear. The sound.
After the sound enters the mike and before it leaves the ear pieces of the receiving WT's, it is no longer sound. It is electro-magnetic signals and waves.
When these waves reach the antenna of a sending WT, they are transmitted as radio waves at the speed of light to the receiver antennae of other WT's. There they are passed through the receivers as electro-magnetic signals and waves until they reach the ear pieces where they are converted into sound.
Sound, by definition, always travels at the speed of sound. And electro-magnetic waves (of which radio waves are a subset) always travel at the speed of light.