New Yorkers getting into taxis these days are being greeted by more than just the overwhelming scent of pine air freshener. Since Aug. 1, cabs have been required to play announcements — prerecorded by such hometown favorites as Jackie Mason and Joan Rivers — that remind passengers to buckle their seat belts and request receipts. ”What we’re trying to do is use a fun gimmick to send a serious message,” says the city’s Taxi and Limousine Commission chairperson, Diane McGrath-McKechnie. But not everyone is thrilled with the injection of star power — especially Gotham’s cabbies, some of whom own their cabs and thus had to pay for the recordings themselves. ”It cost me $75,” grumbles one disgruntled hack. ”We’re giving these celebrities free advertising at our expense.” Customer response has also been mixed. ”The noise interferes with them talking,” notes driver Francisco Panchana, who hears Placido Domingo’s sonorous tenor more than 100 times a day. For its part, the TLC says that the cost was kept as low as possible and that safety is the ultimate goal. Safety in a New York cab: Now, that would be an innovation.