A NOVEL METHOD TO DETERMINE THE ACOUSTIC-IMPEDANCE OF MEMBRANE MATERIAL

A new method is proposed for the determination of acoustic impedance o f a material present in the form of a membrane. It has been successful ly tried on two different types of polymer membranes, viz. PMMA membra ne of thickness 0.20 mm and PET membrane of thickness 0.02 mm. Signifi cantly, the method does not require the knowledge of either ultrasonic velocity or thickness or density of the membrane. It is based on the measurement of magnitudes at two different frequencies in the frequenc y spectra of double through-transmission signals with and without the membrane.