Experimental Study of Acoustic and Thermal Performance of Sound Absorbers with Microperforated Aluminum Foil

Aluminum foil applied to the surface of sound absorbing materials has broad application in the automotive industry. A foil layer offers thermal insulation for components close to exhaust pipes, turbo chargers, and other heat sources in the engine compartment and underbody. It can also add physical protection for acoustic parts in water-splash or stone-impingement areas of the vehicle exterior. It is known that adding impermeable plain foil will impact the sound absorption negatively, so Microperforated Aluminum Foil (MPAF) is widely used to counteract this effect. Acoustic characteristics of MPAF can be modeled analytically, but deviation of perforation size and shape, variation of hole density, material compression, and adhesive applied to the back of the foil for the molding process can impact the acoustic and thermal insulation performance. Because we cannot rely on analytical tools to generate accurate performance of these materials in a production environment, this paper will focus on the acoustic and thermal experimental characterization of these materials. Studies were conducted on flat test samples which have commonly used MPAF applied to the top surface. Results are presented showing the effects of the hole perforation size and density on the acoustic and thermal performance. Results are compared with sound absorbers with other facing materials. Conclusions from this investigation provide guidance for the selection of MPAF during the sound absorber development.