Series and parallel coupling of 3D printed micro-perforated panels and coiled quarter wavelength tubes

Micro-perforated panel sound absorbers are widely used in noise control applications in the fields of architectural acoustics and transport acoustics. Combining micro-perforated panels with other resonant or sound absorbing systems may broaden the frequency range in which they absorb sound while ensuring that large sound absorption values are reached. In this work, a hybrid sound absorber that combines a micro-perforated panel and a coiled quarter wavelength tube is proposed. Series and parallel configurations of these two systems are studied from analytical, numerical, and experimental point of views. A comparison of two three-dimensional (3D) printing techniques for the production of samples highlights the main challenges for the practical implementation of the proposed design. The advantages and limitations of series and parallel arrangements are discussed and while the parallel configuration is more complex to setup in practice, it provides an improved sound-absorbing performance compared with the series configuration. Finally, the reproducibility of the hybrid absorber in parallel configuration is confirmed by testing samples that were produced with two different 3D printers and in two different laboratories.