Could you please provide more info ?
Was this on community server (Browse Servers) or MatchMaking server (Find Game) ?
Was this during pre-round, or during actual round ?
Are you certain it was radio or did you just hear proximity broadcast ? (As suggested by user "jensiii")
@Arc is was on the MatchMaking servers during an actual round.
The name of someone of the opposite team lit up in the left bottom corner with the team color of the opposite team as normal radio communication would.
The soundeffect was clearly radio and not nearby broadcast (non-directional)