Blast/impact frequency tuning and mitigation

A protective device for mitigating stress waves resulting from a blast or impact, said protective device comprising:

• a first layer having a thickness, h1, and having a first acoustic impedance, being made of a linear-elastic material having a first modulus, E1, and a first density, ρ1;
• a second layer having a second acoustic impedance being made of an elastic material having a second modulus, E2 and a second density, ρ2, said second acoustic impedance being less than said first acoustic impedance such that a ratio of the first acoustic impedance to the second acoustic impedance being expressed as √{square root over (E1ρ1)}>>√{square root over (E2ρ2)} and is greater than seventy (70), said second layer being proximate to said first layer along an interface, said first layer and said second layer are collectively configured to tune the stress waves resulting from the blast or impact to a specific tuned frequency of f1=√{square root over (E1/ρ1)}/2h1 with a portion of the stress wave being reflected back toward the first layer at the interface and a portion of the stress wave at the specific tuned frequency being transmitted through the second layer, the reflected portion of the stress wave being greater than the transmitted portion of the stress wave;
• and
• a third layer being made of a visco-elastic material having a critical damping frequency that matches the specific tuned frequency, said third layer being proximate to said second layer and receiving and dissipating the transmitted portion of the stress wave, the third layer being configured such that a period of the critical damping frequency is substantially equal to a time for the reflected portion of the stress wave to traverse the first layer, with a ratio of an unrelaxed modulus to a relaxed modulus of the third layer being greater than ten (10), and a thickness, h3, being greater than five (5) times the wavelength of the tuned stress wave in the third layer so as to ensure significant damping.