$$\require{cancel}$$
This section allows you to see and manipulate the modes for a square drum head. You can change the modes using the sliders to change the mode numbers $$n$$ and $$m$$. For a membrane there are nodal lines which do not vibrate similar to the nodes we saw on the string but now in two dimensions. You can rotate and enlarge the surface by dragging the mouse over the image. Just like the case for a vibrating string, more than one mode can be present on the two dimensional surface at the same time.