The resonance frequency of a panel may be increased by using stiffening ribs, but the
increase that may be achieved is generally quite limited. For stiff enclosures with high
resonance frequencies, materials with large values of Young's modulus to density ratio, E/p are
chosen for wall construction, and for massive enclosures with small resonance frequencies,
small values of E/ are chosen. In practice, stiff enclosures will generally be restricted to small
enclosures.