Resonances are important primarily in smaller rooms where the dimensions of the room may only be up to a few wavelengths long for the lower audio frequencies. One place where resonances almost always appear is in the bathroom, particularly in a shower. This is because the walls are parallel and of highly reflecting materials such as glass or tile. A resonance can occur whenever any dimension of the room is any multiple of one half-wavelength long for some particular frequency. There will be a node at each wall, and the wave will resonate as though it were in a tube closed at both ends. There can be a large number of resonance in each of the three dimensions.