Calculation of the impedance of the matching layer. The transducer will be resonant for a wavelength equal to twice the thickness, which translates to a frequency equal to the speed of sound divided by twice the thickness.Ī basic transducer is composed of three parts, the backing, the piezoelectric crystal, and a matching layer, as shown in figure 1.įigure 2. The resonant frequency of the transducer depends on the thickness and speed of sound in the transducer. Values for some piezoelectric transducer materials. Among all the piezoelectric materials, PZT has the highest piezoelectric stress coefficient which yields higher acoustic power with the same electrical power input. Each piezoelectric material has its own unique properties as shown in Table 1. The piezoelectric property of PZT allows it to change an electrical excitation into motion and pressure, the two necessary elements of acoustic waves.īesides PZT, there are other piezoelectric materials that can be used for transducers. Lead zirconate titanate (PZT) is the most commonly used piezoelectric material in ultrasound transducers. Piezoelectric materials have the ability to generate an electrical potential to an applied mechanical stress and vice versa. A device such as a piezoelectric crystal or a ceramic is needed to convert the electrical power into acoustic power. Most signal generators output signals in electrical form because this is the most convenient way to modify and output the signal. Ultrasound is a cyclic acoustic pressure wave that has a frequency above that of human hearing.

Piezoelectric ultrasound