The Piaggio Avanti normally turns heads because of its unconventional configuration but now it's attracting the attention of noise-conscious Naples, Fla., for its unconventional sound. The Naples Airport Authority is working with Avantair, a fractional and charter company that operates the Italian twin turboprop pusher, to minimize the impact of the unique noise it makes. It's not that the Avanti is particularly loud. In fact, according to FAA measurements (PDF - small print, so be ready to use the "zoom" feature in your PDF reader), there are plenty of aircraft that emit more decibels. However, the configuration of the Avanti, according to a Wikipedia entry, results in the wing wake and engine exhaust hitting the props to create a square wave noise. The unscientific description offered by Alan Parker, chairman of the airport authority's technical committee, is that the Avanti is "irritating loud" with a high pitch he likens to fingernails on a chalk board.
This is a companion discussion topic for the original entry at https://www.avweb.com/news/naples-targets-piaggio-noise