Imagine a two-dimensional system in which a sinusoidal waveform is excited at the exact center of a circular plate. The standing wave pattern is established when the excited wave two-dimensional waveforms for a stable equilibrium pattern of constructive and destructive interference with the reflected waves from the edge of the circular plate (a good way to visualize this might be to consider the behavior of ripples in a pond reflecting from a barrier that forms an exact circle around the point where the ripples were excited).
Draw what you expect the standing wave patterns to look like in this two-dimensional system for increasing resonant harmonics, and explain what characteristics of the oscillating plate affect the value of those resonance frequencies, and what geometric properties of the plate affect the patterns.