Investigation of a dynamic active/passive noise cancellation of polyborosiloxane thin membrane gel.

This study proposes a multifunctional, thin membrane gel based on a formulation of PDMS and boron. The proposed gel offers a dynamic passive stimuli-responsive sound absorption at low frequencies, which can be transformed to active noise cancellation with the use of a secondary sound source. The passive behaviour of the proposed material is the result of a dynamic phase transition in the material’s polymeric network, activated by the interaction with the travelling sound pressure wave. The presence and extent of the phase transition in the material was investigated via Fourier transform infrared spectroscopy and oscillatory rheological measurements, where it was found that the amount of boron in the gel has a crucial role on the occurrence of the phase transition and consequently on its acoustic performance. The passive scenario results revealed a high and dynamic absorption of approximately 80% at the absorption coefficient peaks, which dynamically shifted to lower frequencies while sound amplitudes were increased. The active noise cancellation was successfully demonstrated at the lower frequencies range, as the occurrence of the phase transition was actively controlled via the sound pressure wave introduced. The aforementioned phase transition was intensified, with energy consumed in this process, resulting in a dynamic noise cancellation. These results demonstrated that the proposed gel membrane material can be used to develop active/passive deep subwavelength absorbers with unique properties, which can dynamically tune their performance in response to external stimuli, and that can be further controlled/activated with the use of mechanical transducers.