@article{oai:jaxa.repo.nii.ac.jp:00034527,
 author = {NAKAMURA, Yoshiya},
 issue = {4},
 journal = {ISAS report/Institute of Space and Aeronautical Science,University of Tokyo},
 month = {Sep},
 note = {Rotational noise which is predominant in helicopter noise is decomposed into thickness noise and loading noise by its cause of generation. It is also divided into near field noise and far field noise by its classification of radiating region. Such decomposition of noise sources and separation of an integral solution of wave equation into integrand and integrating region made it possible to predict noise characteristics analytically. The integrating region named "influential surface" can be determined once observer position and time are specified. All noise sources which will bring the pressure change at the observer simultaneously are distributed in this region. The influential surface changes its shape dynamically, because the relative velocity of the blade element to the observer varies over the rotor disk. The magnitude of near field noise is propotional to the area of the influential surface and that of far field noise is propotional to its time derivative. By these decompositions of the integral expression of pressure change it has become possible to predict analytically many noise characteristics such as wave form, noise level, spectrum, and so on, as the function of rotor parameters. Some methods of noise reduction have been proposed based on a parametric study. The thickness noise is considered to have fairly high noise level and to be one of potential cause of blade slap. The analytical study of the effect of blade-vortex interaction on the slap has been left for future investigation., 資料番号: SA2401268000},
 pages = {111--151},
 title = {The Analysis of Helicopter Roter Noise},
 volume = {42},
 year = {1977}
}