Method of making sound absorbing laminates and laminates having maximized sound absorbing characteristics

A laminate having maximized sound absorbing characteristics, comprising:

• a) a porous insulation substrate having an air flow resistance less than that required to produce an optimum sound absorbing characteristic for said substrate;
• and
• b) a thin, semi-porous facing superimposed upon a face of said substrate, said facing having an acoustic resistance ratio that when superimposed upon said face of said substrate, a laminate is formed having an acoustic resistance ratio that approximates or equals the optimized value of the acoustic resistance ratio for said substrate.

A laminate having optimized sound absorbing characteristics comprising:

• a) a porous insulation substrate having an air flow resistance less than that required to produce an optimum sound absorbing characteristic for said substrate;
• and
• b) a thin, semi-porous facing superimposed upon a face of said substrate, said facing having an acoustic resistance ratio that approximates or equals to the difference between the acoustic resistance ratio of said substrate and the optimized value of the acoustic resistance ratio for said substrate.