1. The problem statement, all variables and given/known data I need this to find the the reflective coefficient and multiply this by 100 to find the percentage of original energy reflected back however i cannot find the acoustic impedance of wool no matter how hard i try. 2. Relevant equations Im using the reflective coefficient formula which reads as ((Z2-Z1))^2/((Z2+Z1))^2 where z is a sound impedance. In this case Z1 is the sound impedance of air and Z2 is the sound impedance of wool. I also found a formula to calcualte acoustic impedance which reads as Z=density of material(pressure*speed of sound through the material) however it doesn't specify whether the pressure is a constant or not and like the acoustic impedance, i also cannot find the speed of sound through wool after all this time. 3. The attempt at a solution Any help or directions to decent sources would be extremely helpful. I know exactly what to do but these lack of values is holding me back from finishing anything else. Any help would be greatly appreciated.