Geometric design and acoustic performance of dihedral focusing retroreflectors based on confocal conics

IF 3.4 2区物理与天体物理 Q1 ACOUSTICS

Applied Acoustics Pub Date : 2025-08-25 DOI:10.1016/j.apacoust.2025.111031

Shuai Lu , Densil Cabrera , Jonothan Holmes

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引用次数: 0

Abstract

This study investigates dihedral retroreflectors, and how they can be modified for increased retroreflection in their vicinity by warping one or both of the dihedron’s surfaces thereby creating a focusing retroreflector. Previous research on this type of focusing acoustic retroreflector was restricted to identical confocal parabolas, and did not theorise the pattern of retroreflection beyond the focus. The present study shows that a wide range of solutions exists, for which retroreflection is particularly strong over a distinctive curve referred to as an auto-caustic, the shape of which can be calculated from the dihedron’s geometric parameters. Five cases were evaluated using raytracing, finite-difference time-domain acoustic simulation, and physical acoustic measurement. The cases include combinations of a confocal ellipse and hyperbola (convex and concave hyperbola), a confocal pair of parabolas, an ellipse and line, and a circle and line. Results highlight the importance of the auto-caustic curve, over which retroreflection is strong and similar to that at the geometric focus. For the cases evaluated (with 1.22 m dihedron face lengths and a focal length of 2 m), focusing retroreflection is particularly evident in the 2 kHz and 4 kHz octave bands.

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基于共聚焦圆锥的二面体聚焦后反射镜几何设计与声学性能

本研究研究了二面体反反射器，以及如何通过扭曲一个或两个二面体的表面来增加其附近的反反射，从而创造一个聚焦的反反射器。以往对这类聚焦声学后向反射器的研究仅限于相同的共聚焦抛物线，并没有理论化焦点以外的后向反射模式。目前的研究表明，存在各种各样的解决方案，其中逆反射在称为自焦散的独特曲线上特别强，其形状可以从二面体的几何参数计算出来。使用光线追踪、时域有限差分声学模拟和物理声学测量对5例进行了评估。这些情况包括共焦椭圆和双曲线（凸和凹双曲线）的组合，共焦抛物线对，椭圆和直线，圆和直线。结果强调了自焦散曲线的重要性，其上的反反射很强，与几何焦点处的反反射相似。对于评估的情况（1.22 m的二面体面长和2 m的焦距），聚焦反射在2 kHz和4 kHz的频带中特别明显。

本文章由计算机程序翻译，如有差异，请以英文原文为准。

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来源期刊

Applied Acoustics 物理-声学

CiteScore

7.40

自引率

11.80%

发文量

618

审稿时长

7.5 months

期刊介绍： Since its launch in 1968, Applied Acoustics has been publishing high quality research papers providing state-of-the-art coverage of research findings for engineers and scientists involved in applications of acoustics in the widest sense. Applied Acoustics looks not only at recent developments in the understanding of acoustics but also at ways of exploiting that understanding. The Journal aims to encourage the exchange of practical experience through publication and in so doing creates a fund of technological information that can be used for solving related problems. The presentation of information in graphical or tabular form is especially encouraged. If a report of a mathematical development is a necessary part of a paper it is important to ensure that it is there only as an integral part of a practical solution to a problem and is supported by data. Applied Acoustics encourages the exchange of practical experience in the following ways: • Complete Papers • Short Technical Notes • Review Articles; and thereby provides a wealth of technological information that can be used to solve related problems. Manuscripts that address all fields of applications of acoustics ranging from medicine and NDT to the environment and buildings are welcome.