New system for the measurement of sound-insertion loss on small samples: a comparison with ASTM-E2611 and ASTM E90 test procedures

This article follows a companion article presented at the SAE NVC 2021, in which a new system for the measurement on small samples of the normal-incidence Insertion Loss (IL) of multilayers used for the manufacturing of automotive sound package parts was first introduced. In addition to simplifying the evaluation of the sound-insulation of multi-layers used to produce sound-package components, the system aims to overcome the limitations of the test procedure based on the ASTM E2611 standard. In this article, the latter point is demonstrated by comparing the insertion loss results obtained with the new system with those obtained with the test procedure based on the ASTM E2611 standard on a few multilayers commonly used for the manufacturing of automotive sound package parts. Results indicate that the results obtained by means of the newly developed system are more meaningful, practically usable and less prone to edge-effects, compared to those obtained according to the ASTM E2611 test procedure. In addition to this, the article compares also the results obtained by means of the new system with those obtained in a two-chamber facility commonly used for the evaluation of diffuse-field insertion loss following the ASTM E90 standard, a quantity customarily employed in the automotive industry for the assessment of the sound insulation of acoustic multilayers. Results indicate that the results obtained with the new system compare well with those obtained with the two-chambers facility, both quantitatively and qualitatively. This indicates that sound-insulation tests with the new system may be a valid alternative to much more resource-consuming tests in two-chamber facilities, in particular (but not only) when the sound insulation of moulded parts must be assessed.