New Sound Absorption Materials: Using Additive Manufacturing for Compact Size, Broadband Sound Absorption at Low Frequencies

This paper discusses the potential of achieving compact size broadband sound absorption at low frequencies, by taking advantage of Additive Manufacturing (AM). Sound absorption systems are widely used for reducing noise and improving room acoustics. However, they are often constrained by conventional design and production techniques; and offer limited options for customising performance and form. Moreover, typical solutions are difficult to use for the damping of low frequencies due to their large size or their narrowband performance. This research suggests that AM may support the development of novel and customisable sound absorbing products of high performance. This can be achieved by focusing on geometry-related sound absorbing mechanisms with geometrical features that are within the manufacturing capabilities of AM. Three new concepts are explored regarding resonant absorbers: (1) a combination of absorbing principles, (2) a combination of multiple resonators and (3) adding resistance at the entrance of the orifice of resonant absorbers. Each concept is digitally designed and produced with Selective Laser Sintering (SLS). To assess performance, small samples are tested in the impedance tube (B&K, type 4206), using the two microphone transfer function method. The results show the possibility of achieving broad peaks at low frequencies.