A Wide Range of Perforations Provide High Transparency
The first test compares the sound absorption performance of a bare, unprotected 4" blanket of fiberglass with the same material protected by sheets of perforated metal that required the sound to pass through the perforated sheet. The three perforated sheets were of the following specifications:
IPA #107 with 48% Open Area
IPA #112 with 37% Open Area
IPA #115 with 23% Open Area
Chart 1 disclosed that there was virtually no diminishment of the fiberglass blanket's sound absorption performance by the presence of any of the perforated metal sheets; they were equally transparent with only minor and insignificant variations. Each of the perforated-protected tests followed very closely the performance of the bare blanket at all frequency levels.
