Study program for lift fan noise reduction and suppression

V/STOL aircraft lift fan noise reduction and suppressio

Sound Attenuation in Acoustically Treated Turbomachinery Ducts Sound Attenuation in Acoustically Treated Turbomachinery Ducts

The paper presents a theoretical development, accompanied by an experimental data check, of the attenuation in acoustically lined ducts with no airflow. The results indicate that the number of spinning lobes, as well as the generation frequency, have a major effect on the performance of the acoustic material. It also was indicated that the impedance components of the acoustic lining can be optimized to give a maximum sound energy reduction over a given range of engine speeds

Low tip speed fan noise demonstration program

Noise level data for low tip speed turbofan engin