Acoustic performance of boundaries having constant phase gradient

Abstract

In this paper, inhomogeneous boundaries having constant phase gradient are investigated. In principle, such a theoretically proposed boundary is dispersionless. In practice, however, when the boundary is realized by a subwavelength-structured tubes array, the impedance discretization brings about sub-reflections at high frequencies. Moreover, determined by the longest duct in the array, a realized boundary is impractically thick. Therefore, a finite-thickness boundary is further proposed by truncating and periodizing the tubes in the array. In this paper, the theoretical analysis agrees well with the numerical simulations. By appropriately choosing its phase gradient and target frequency, the finite-thickness boundaries have potential applications in noise control.

Sound trapping and dredging barriers

“…3(c), such gradient surfaces are achieved by the slender tubes array with progressively tuned length and periodical transcation. 11 The same gradient absolute value indicates that, for these two types of barriers, the construction of the barrier inner surfaces by the tubes array is identical except arranged in reverse. This means that we can further enhance the performance of the well-designed STBs by simply assembling their inner surfaces "upside down.…”