Draw a shape, hear it as a drum: Eigendrum solves the wave equation in your browser

Eigendrum lets you draw any closed shape and hear its vibrational modes as a real drum. It numerically solves the eigenvalue problem −∇²u = λu with zero boundary conditions using finite elements, and is tested against known spectra for circles and rectangles. Striking different spots excites different mixtures of modes, and you can even play individual modes alone. The site includes two isospectral drums (Kac's question answered 'no'), and lets you define shapes via parametric equations. No backend: everything runs client-side.