Theory And Experimental Research Of The Push-pull Infrasound Source

At first,this thesis studies a new method to generate infrasound which is referred to as separated pull-push flow modulation.The relations among the pressure of vocal tract of the sound source,air velocity and the modulation area are deduced by the theory of air flow field of modulation air sound source.The new type air-modulated speaker with push-pull concept is investigated to determine the improvement on efficiency when comparing with classical air-modulated speaker.A horn can improve the sound radiation of the sound source.The general expression of sound pressure of exponential horn and conical horn can be used to provide a theoretical guidance for the simulation modeling and sample design.We have designed a new type of "tee cavity" push-pull infrasound source on the basis of the original push-pull infrasound source.The new sound source with better air volume and smaller volume have a better performance in radiation acoustic energy.Secondly,the simulation model of the Separated push-pull infrasound source is established.The simulation analysis of the sound source internal flow field of the static pressure distribution and the distribution of air velocity along with the modulation cycle can prove that sound the energy conversion efficiency have improved as the sound source working like a monopole.The simulation model of exponential horn and conical horn can calculate their transmission loss curve,which show their working performance of low frequency.It can provide feedback for the design of the sound horn.Finally,some experiments about tee cavity push-pull infrasound source have been conducted.Compared to the response characteristic curve,the harmonic number and size of the three source separately working in the single pump,double pump and separation of push-pull,we come to a conclusion that the tee cavity push-pull infrasound source has the best performance.