The Hyundai Sonata Hybrid won’t be coming to the United States as early as expected. The hybrid version of Hyundai Motor’s Sonata mid-size sedan will not reach U.S. dealerships until late this month or early April, the automaker’s U.S. branch announced on Saturday. Hyundai had planned to release the vehicle in January this year but decided to postpone the launch to change its virtual engine sound system. Electric cars and hybrids do not make enough engine noise at low speed to make pedestrians aware of their approach. Under a U.S. law signed in January, automakers must gradually add devices to their hybrid cars that emit artificial engine sounds. The National Highway Traffic Safety Administration is currently writing up the specific rules. Hyundai is altering its noise device to boost the volume and remove a switch to turn it off. The Sonata Hybrid will be shipped to the U.S. from the automaker’s plant in Ulsan. After its debut in the U.S. it will roll out to other markets, including Korea in June.