A feasibility study is presented on the application of riblets to suppress turbulent pressure sources leading a reduction in generation aerofoil self-noise. It shown that can reduce skin friction as well turbulence intensity inside boundary layer. In addition, near-wall structures were found be dissipated quite rapidly when crossing surface. (1) slightly wall fluctuating power spectral density ...

noise is one of the main parameters to be considered to achieve a healthy indoor ambience in ferries. therefore, the noise standards need to be more specialized and specifically based on real sampled data and case studies. in the present research, the noise levels in a ship, under different working conditions, were sampled and compared with those specified in the new and old standards. an initi...

background : cement industry has many process units. basically all of these units can be considered as a source of noise. since noise pollution is defined based on its offensive hearing effects, the importance of the noise sources depends directly on the number of workers in the unit.   materials and methods : an experimental study has been done at tehran cement factory to recognize and analyze...

The menace of noise is a by-product of civilization and its hazards are well known. Noise levels were measured in Karachi, at different places and at different times of the night and day, using an Amplaid noise meter. The leg for Karachi came to 80 dB (A), the General Noise Index x (G.N.I.) to 460, and the noise pollution level (N.P.L.) to 99 dB (A). These values are significantly higher (P les...

  Background : Cement industry has many process units. Basically all of these units can be considered as a source of noise. Since noise pollution is defined based on its offensive hearing effects, the importance of the noise sources depends directly on the number of workers in the unit.   Materials and Methods : An experimental study has been done at Tehran cement factory to recogn...