According to BWS2017
after partner made a preemptive opening bid in silent auction - a direct bid of new suit (but not 4♣) by responder at game level of the suit in which the opening bid was made is asking bid for control in specified suit.
According to above definition all responses here :2♥-4♦; 3♥=4♦ ; 3♠=4♦;3♥-4♠; 2♠-4♥; 3♠-4♥; and some more are all asking bids.I have no problem with that concept. Not sure I like to play that 3♠-4♥ should also be played as asking bid;
How you think 4♥ should be interpreted after 3♠-4♥
Plus... it's free!