Cruise noise of an advanced counterrotation turboprop measured from an adjacent aircraft

Acoustic test results are presented for a full-scale counterrotation demonstrator engine installed on a Boeing 727 aircraft in place of the right-side turbofan engine. Sideline acoustic data were acquired from a Learjet chase aircraft instrumented with noise and wing-tip flush mount microphones. Data are presented for a 47.2-m sideline at several engine operating conditions and flight Mach numbers of 0.50 and 0.72.