Noise reduction methods of modern helicopter manufacturing

In the early days of helicopter manufacturing the main purpose was to develop the performance of helicopters and they didn't take into consideration such problems as the high noise emission. But nowadays the new local and international stricter noise certification standards have made it the hottest issue for helicopter manufacturers. Growing public sensitivity to helicopter noise has forced the major rotorcraft manufacturers to be innovative in reducing measured and perceived external noise levels of their products. We can say that they have successfully solved many of their problems and use a variety of technologies and design solutions to reduce noise. In this work we would like to present these new ways in helicopter design and to highlight their positive effects.