Figure 16 Different backing cavity configurations considered. The frequency-averaged absorption is plotted verses effective porosity in Figure 17. First of all, it was observed that the average absorption was much higher for cases where a backing substrate was utilized. It was also notable that the location of the maximum value for frequency-averaged absorption varied depending on the backing substrate used. Accordingly, it is best if the effective porosity of the MSP is optimized for a particular backing substrate. Figure 17 Frequency-averaged sound absorption coefficients for MSP absorbers with different backing substrates. Sound absorption (measured in a manner similar to ASTM-C423) in one-third octave bands is shown for the four different backing cavity configurations in Figure 18. In each case, an MSP was chosen with an effective porosity that would maximize the frequency-averaged absorption (according to Figure 17). The results clearly demonstrate that the combined MSP and backing substrate substantially improves the sound absorbing characteristics over the entire frequency range when compared to an MSP without backing. Most importantly, the sound absorption is clearly improved at nearly all frequencies. It should be noted that lower frequency absorption could be achieved by further increasing the backing cavity depth. Though increasing the cavity depth would increase the amount of volume occupied by the absorber, it would only marginally increase the cost.
Figure 16 Different backing cavity configurations considered. The frequency-averaged absorption is plotted verses effective porosity in Figure 17. First of all, it was observed that the average absorption was much higher for cases where a backing substrate was utilized. It was also notable that the location of the maximum value for frequency-averaged absorption varied depending on the backing substrate used. Accordingly, it is best if the effective porosity of the MSP is optimized for a particular backing substrate. Figure 17 Frequency-averaged sound absorption coefficients for MSP absorbers with different backing substrates. Sound absorption (measured in a manner similar to ASTM-C423) in one-third octave bands is shown for the four different backing cavity configurations in Figure 18. In each case, an MSP was chosen with an effective porosity that would maximize the frequency-averaged absorption (according to Figure 17). The results clearly demonstrate that the combined MSP and backing substrate substantially improves the sound absorbing characteristics over the entire frequency range when compared to an MSP without backing. Most importantly, the sound absorption is clearly improved at nearly all frequencies. It should be noted that lower frequency absorption could be achieved by further increasing the backing cavity depth. Though increasing the cavity depth would increase the amount of volume occupied by the absorber, it would only marginally increase the cost.
Activities%20and%20Findings.docx