Turbulent pressure fluctuations can compromise the accuracy of far-field acoustic measurements when microphone arrays are flush-mounted on surfaces exposed to fluid flow. To address this, recent advances in acoustic metamaterials have introduced novel approaches to enhance the signal-to-noise ratio of these measurements. In this paper, new techniques for coupling the sound and flow field to a meander metasurface are discovered through computational acoustics modeling and examined through wind tunnel testing in Virginia Tech’s Subsonic Modular Anechoic Research Tunnel (SMART). The results provide insight into the optimal shape for allowing sound waves into a metamaterial while attenuating turbulent boundary layer noise.
GleggSAL. The accuracy of source distributions measured by using polar correlation. J Sound Vib1982; 80(1): 31–40.
5.
SodermanPTNobleSC. Directional microphone array for acoustic studies of wind tunnel models. J Aircraft1975; 12(3): 168–173.
6.
ShinHGrahamWRSijtsmaP, et al.Implementation of a phased microphone array in a closed-section wind tunnel. AIAA J2007; 45(12): 2897–2909.
7.
StokerRGuoYStreettC, et al.Airframe noise source locations of a 777 aircraft in flight and comparisons with past model–scale tests. In: 9th AIAA/CEAS Aeroacoustics Conference, Hilton Head, SC, USA, 12–14 May 2003AIAA 2003–3232, 2003.
8.
JonesMG. A comparison of signal enhancement methods for extracting tonal acoustic signals. NASA TM-1998-208426. NASA Langley Research Center, 1998. URL:. https://ntrs.nasa.gov/citations/19980201049
9.
KirbyGJ. The effect of transducer size, shape and orientation on the resolution of boundary layer pressure fluctuations at a rigid wall. J Sound Vib1969; 10(3): 361–368.
10.
JaegerSMHorneWCAllenCS. Effect of surface treatment on array microphone self-noise. In: 6th AIAA Aeroacoustics Conference and Exhibit, Lahaina, HI, USA, 12–14 June 2000AIAA, 2000, pp. 2000–2193. DOI: 10.2514/6.2000-1937.
11.
DamaniSDevenportWJAlexanderWN, et al.Kevlar-covered subresonant pressure sensor for flow measurements. AIAA J2025; 63(8): 3365–3374.
12.
DamaniSButtHBanksJ, et al.Low-wavenumber wall pressure measurements in zero-pressure gradient boundary layer flow. In: AIAA SciTech 2022 Forum, San Diego, CA, USA, 3–7 January 2022AIAA, 2022, pp. 2022–2795. DOI: 10.2514/6.2022-1795.
13.
VanDercreekCMerino-MartinezRSijtsmaP, et al.Evaluation of the effect of microphone cavity geometries on acoustic imaging in wind tunnels. Appl Acoust2021; 181(1): 108154.
14.
DamaniSAlexanderNDevenportWJ, et al.Excitation of airborne acoustic surface modes driven by a turbulent flow. AIAA J2021; 59(12): 5011–5019.
15.
BraatenEDamaniSAlexanderN, et al.Directionally sensitive sensor based on acoustic metamaterials. In: AIAA AVIATION 2023 Forum, San Diego, CA, USA, 12–16 June 2023AIAA, 2023, pp. 2023–3828. DOI: 10.2514/6.2023-3828.
16.
GalluscioCADamaniSAlexanderWN, et al.Locating sound through turbulence with novel array designs. AIAA J2025; 63(12): 5381–5392.
17.
AssouarBLiangBWuY, et al.Acoustic metasurfaces. Nat Rev Mater2018; 3: 460–472.
18.
BeadleJGHooperIRSamblesJR, et al.Broadband, slow sound on a glide-symmetric meander-channel surface. J Acoust Soc Am2019; 145(5): 3190–3194.
19.
LuJQiuCKeM, et al.Directional excitation of the designer surface acoustic waves. Appl Phys Lett2015; 106(20): 201901.
20.
DoughertyRP. Functional beamforming. In: 5th Berlin Beamforming Conference, Berlin, Germany, 19–20 February 2014BeBeC–2014–01, 2014.
21.
AmietRK. Refraction of sound by a shear layer. J Sound Vib1978; 58(4): 462–482.
