I was reading about piezo elements and its frequency.
I found on the internet that : The composition of the ceramic material and the shape and volume of the element determine the resonance frequency -- generally, a thicker element has a lower resonance frequency than a thinner element of the same shape. Determining Resonance Frequency
I found also that : At ultrasonic frequencies large surface area parts draw considerable current and resistive heating of the electrodes becomes the limiting factor. Piezo Systems - Frequently Asked Questions
First question, does that mean that if the piezo element is circular has a different frequency as a rectangular piezo element plate when they have the same thickness?
I know that frequency = velocity/(2*thickness)
My second question, what is the relation between frequency of piezo element and its shape?