METHOD OF MEASURING SPEED OF ULTRASOUND Russian patent published in 2012 - IPC G01N29/00 

FIELD: physics.

SUBSTANCE: ultrasonic pulses are transmitted the inspected material, wherein the ultrasonic pulses are transmitted with filling frequency ν₁ through a sample of the analysed material initially without loading at a given temperature; the speed of ultrasound C is measured at the same temperature; a series of ultrasonic echo signals reflected by particles in any of two inner regions of the material are then obtained; said series is picked up by two receiving piezoelectric sensors which do not touch the outer surface of the material and lie in an immersion medium; that series is decomposed into a Fourier time series with repetition period T₂ of ultrasonic pulses; the pulse repetition frequency ν₂=1/T₂ is varied; a value ν₂ is achieved, where the amplitude values of even harmonics of the Fourier series are not equal to zero and phases of these harmonics undergo a jump of π radians; the speed of ultrasound C is then compared with that pulse repetition frequency ν₂; temperature of the analysed material is raised or lowered and the speed of ultrasound C is once more compared with the pulse repetition frequency ν₂; the dependency of pulse repetition frequency ν₂, where phases of even harmonics undergo a jump of π radians, on the speed of ultrasound S is determined, after which the speed of ultrasound S in the inner regions of the analysed material under a load is determined from the dependency of that pulse repetition frequency ν₂.

EFFECT: high accuracy of measuring speed of ultrasound in inner regions of material.

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