Per wikipedia:twinkess wrote:The B717s are actually a bit quieter than the DC-9s, however most of the planes you are seeing are their older siblings the MD-88s and MD-90s. Still powered by the JT8D engines that made the DC-9s soooo loud.
The MD-90 is a mid-size, medium-range airliner that was developed from the MD-80 series. It is a 5 feet (1.5 m) longer, updated version of the MD-88 with similar electronic flight instrument system (EFIS) and more powerful, quieter and fuel efficient IAE V2500 engines instead of the JT8D engines, which power the MD-80 series. This made the MD-90 the first derivative variant of the DC-9 to use a high-bypass turbofan engine.