Vertical - Bending Mode Conversion Air Transducer Circular Bending Vibration Emitters

Because tbe specific acoustic impedance of transducer and air is unmatched.Air-borne thansducer kasn't been developed very wen for a long time. Transducerand air are so difficult in impedance matching. The radiation efficiency of airbornetransducer was very low. It results in its limited use in practice. Nowadays, peopIehave two methods on impedance matching. First, by using the match layer of halfwaveIength, the radiation efficiency of airborne transducer was improved. Second,by using flexural vibration mode, the difficult in impedance match was improved insome degree. Gallego in Spain had first designed flexural vibration transducer. Itoffers to the vibrating system a good inipedance match to the propagatiou mediumaud consequently it improves thc over-all effiency of the transducer. Moreover itowus the vidses of complex role. But, Gallego only studied it in the experiment. Inthis paper, the writer studies the flexuraI vibration airborne transducer bothexperimentally and tbeoretically.(l) using the theory of thin plate's flexural vibration, the resonance frequencyequations of the plate with dtherent vibration mode and boundary condition arederived. The resonance frequency of different vibration mode is also derived at acehain condition.(2) The expression of plate's radiation pressure and radiation pattern withdifferent boundary condition are derlyedp=-ω.ω₀ρ₀/exp[j(ω₀t-k₀r)]{Aa/k²-k₀²sin²θ[-k₀sinθJ₀(ka)j₁(k₀asinθ)+kj₀(k₀asinθ)j₁(ka))]+Ba/k²+k₀²sin²θ[k₀sinθI₀(ka)J₁(k₀asinθ)+kj₀(k₀asinθ)I₁(ka)]}Also the formula of radiation ptuern i8 modified. Becau8e axi8 pres8ure of thenexural vibrahon plate are zero, it can't u8e the expres8ion of theditional radiationpattern. It isD, == XPmaxTke radiatiou patt6rn of tbe pIat6 at dchrent boundary conditiOn are 8boulat6d hycomputer which are in good agreement witk GanegO's measured radiation pattern.(3) The boetic energy of plate with dtherent boundary condthen i8 obtained byusing the method of energy. The expre88ion of equicalent ma8s can be obt8ined frOmthe haetic energy, and the equivalent capacitance frOm the equivalent ma88.(4) The thin circular plate's radiation impedance witb different boundary conditionis derived.(5) The resonance frequency of plate under different boundary condition ismeasured. Measured re8ult8 are the same as tbeory value, whicb proves that thetheory i8 correct.(6) From the theory, we can work out the 8tepped pIat6's radiation pattern audradiation bopedance. It 8kow8 that the experiment8l radiatiOn pattern of steppedplate is in agreement witb the 8imuIated result.