Contribution to the Study of the Acoustic Air-Jet Generators

A thorough analysis of previous papers leads one to explain the operation of the acoustic air-jet generators, outside the region or in the absence of the Hartmann instability intervals, through the periodical boundary layer separation developed on objects placed in the air-jet. A new type of generator, working in these conditions, the “needle” generator is described. It is experimentally shown that its characteristics are great emission stability, high acoustical efficiency (up to 16%) and a purity of the emitted sound which can be as high as 99%.