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Metamaterials can provide many engineering applications such as vibration attenuation and heat flux cloaking. However, the problems of isolating elastic waves and directing heat flux via a metamaterial device have not been resolved completely yet. In this paper, a dual-functional metamaterial, with cylindrical stub periodically attached on the multilayered plate, is initially designed and investigated numerically and experimentally. Numerical results demonstrate that the elastic wave band gaps can be opened and tuned effectively with the evolution of the rotation angle of the matrix plate.

The protection efficacy of facemasks and respirators has been well documented. The change of human nasal functions after wearing N95 respirator and surgical facemask is not known. In a parallel group study, we recruited 87 healthy healthcare workers. Each of the volunteers attended two sessions, and wore N95 respirator in session 1 (S1) and surgical facemask in session 2 (S2) for 3hours. Mean minimum cross sectional area (mMCA) of the two nasal airways via acoustic rhinometry and nasal resistance via rhinomanometry were measured before and immediately after the mask wearing.

Face masks or respirators are commonly worn by medical professionals and patients for protection against respiratory tract infection and the spread of illnesses, such as severe acute respiratory syndrome and pandemic influenza (H1N1). Breathing discomfort due to increased breathing resistance is known to be a problem with the use of N95 respirators but there is a lack of scientific data to quantify this effect. The purpose of this study was to assess objectively the impact of wearing N95 face masks on breathing resistance.

There is growing interest in the development of path coiling-based labyrinthine acoustic metamaterials for realizing extraordinary acoustical properties such as low-to-mid frequency sound absorption. We present a subwavelength labyrinthine acoustic metastructure (≤ ≤ 3 cm) exhibiting a superior sound absorption with a high bandwidth (more than one octave in the range of 400–1400 Hz).

The carbon dioxide level within N95 respirator is higher than without it, which needs a mechanical explanation. In the current study, we built a three-dimensional (3D) model of normal human nasal cavity to simulate the volume of fraction of both fresh air and respired air within the nasal cavity. The model consists of large rectangular domain outside the nasal cavity representing ambient air, human nasal cavity and partial of the pharynx. Two cases were simulated. Case I refers to a human face with a N95 respirator onto human face, and case II refers to a human face without a respirator.

The conflict between the acoustical performance and ventilation efficiency in conventional noise barriers limits their application potentials in several settings. To address this challenge, we design and experimentally demonstrate a ventilated tunable acoustic metamaterial for noise mitigation at targeted frequencies. Through the structure, a peak normal incidence sound absorption coefficient of more than 0.96 at 1000 Hz and the peak normal incidence sound transmission loss of 18 dB is achieved while maintaining the air circulation with a 45% open area of ventilation.

By Yu Zhou and Lihua Jin