Determination of acoustic performance parameters of insulation materials in conditioned medium

Acoustic performance parameter tests are required to be performed in order to select suitable method or material to provide sound insulation in many sectors and applications like construction, heating, ventilating, white goods, automotive, aeronautical. These performance parameters are sound absorption coefficient, surface impedance, insertion loss, noise reduction and transmission loss. Generally, special acoustic rooms or special measurement systems are required for determining the performance parameters. Impedance tube system is the most commonly used apparatus that was also standardized in ISO and ASTM measurement standards. This system enables to determine the performance parameters via processing the sound pressures based on standing wave principle in a tube. Today, determination of acoustic performances of insulation materials under operating conditions is requested especially from automotive and aeronautical industries. Standard impedance tube systems are not able to simulate operating conditions such as the humidity and the temperature of the medium. Specially-conditioned acoustic rooms as an alternative can be quite expensive. In this study, an impedance tube apparatus that meet with related standards and with conditioned medium is designed and produced for insulation materials. Designed apparatus has a sandwich composite construction; therefore, it is lighter than existing ones, quite stiff and it has less sound leakage. Moreover, with this new system having a conditioner unit, it is available to make tests for the insulation materials under different humidity and temperatures of the medium and specimen. In addition to that, the new apparatus has a design and measurement capability to measure random incidence acoustic parameters with a rotating specimen apparatus. By this apparatus, acoustic performance parameters of several insulation materials are determined in the cases of random incidence angles and under varied air conditioned. In this regard, incident and random absorption coefficients of several samples of isolation materials are measured under conditioned medium and presented to the literature as a benchmark study.