"The introduction of aircraft with advanced counter-rotating open rotor (CROR) powerplants will improve specific fuel consumption by 10-15% relative to equivalent turbofans. The NINHA project will assess whether noise issues away from airports (i.e. during high altitude operations) will hazard the introduction of this new generation of powerplants designed to improve fuel burn and reduce CO2 emissions beyond the ACARE 2020 objectives.In the 1980’s prototypes of the first generation of open rotor engines were developed and tested. One of the findings was that the noise generated by these engines, even in the en-route flight phase, was significant, thus hazarding public acceptance. Since then significant effort was dedicated to improve their aeroacoustic design and the new generation of CROR engines currently envisaged are much quieter than their predecessors. The EU DREAM programme is addressing the noise of CRORs around airports; NINHA addresses en-route noise.Existing long-range noise prediction models and CROR noise source prediction models will be developed in NINHA for their application to the prediction of en-route noise levels, and validated with A400M flight data and CROR noise data obtained in projects like DREAM.Since aircraft might be audible en-route in areas with very low background noise levels, a review will be performed in NINHA of issues such as noise metrics, annoyance and perception. EASA have agreed that their recent study on en-route noise levels of current aircraft can serve as a reference for the NINHA project, allowing a comparison with the predicted en-route noise of advanced CRORs. Based on the findings in NINHA, recommendations will be given to ICAO/CAEP on possible future en-route noise evaluation processes."