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the refraction of glass to create fiber-optic, mandrel-based hydrophones that are currently employed for underwater sensing used by the military and the oil and gas explora- tion industry (Bucaro et al., 1977; Cole et al., 1977) as well as microelectromechanical (MEMS) acoustic microphones that are now widely used in nearly every device that mea- sures sound (Hohm and Sessler, 1983).
As evidenced by the seminal contributions listed above, the nature of the research conducted by members of the TCEA is inherently cross-disciplinary. Indeed, the TCEA embod- ies this from both technical and professional standpoints, bringing together groups of scientists and engineers from a wide range of backgrounds, training, expertise, and inter- ests. The TCEA membership list includes people in large research universities and small liberal arts colleges, private industry, and the military, each bringing their individual experience and training to bear on emerging technical and scientific challenges in acoustics. Although this breadth of expertise and interests is generally valuable, it also repre- sents a challenge because many members are also active in more specialized organizations or may work on topics that can be difficult to share with the scientific community due to intellectual property restrictions. The TCEA has recently been trying to bring these communities back to the ASA through the organization of special sessions and extending speaking invitations to prominent researchers.
The wide range of interests in the TCEA community makes it hard to identify a subset of recent works that have been especially impactful. Instead, I have selected a few representative recent contributions to The Journal of the Acoustical Society of America (JASA) to provide a window into the quality and breadth of research that falls under the umbrella of engineering acoustics.
The first is recent work by Cheer et al. (2019) who inves- tigated the concurrent use of reference microphones in both the left and right ears to improve the performance of headphones with active noise control. Their results showed that the strategy of using dual reference signals requires an increased computational demand but affords a significant control advantage for noise sources originating from the side of the user while maintaining performance for noises originating from the front or back.
Another recent work by researchers at ETH Zurich used experiments and numerical modeling to investigate the
use of a novel signal-processing approach known as mul- tidimensional deconvolution to postprocess data from acoustic-scattering experiments to remove reflections from the laboratory boundaries, leaving only the Green’s func- tions of a scattering object (Li et al., 2021). This approach is highly valuable to acoustics research across application areas and may ultimately help enable researchers to “embed” physical experiments in computational domains to study the interaction of targets with arbitrary environments using a single experimental apparatus (Becker et al., 2018).
The final highlighted work is recent experimental and computational research by Jeon et al. (2021) that used X-ray computed tomography (CT) scans combined with convolutional neural networks (CNNs) to estimate the transport parameters of fibrous materials used as acoustic absorbers. The transport parameters and sound absorp- tion coefficients of the fibrous volume predicted by the CT-informed CNN models showed good agreement with the measured values, which demonstrates the valuable integration of advanced measurement technology and analysis using novel computational methods to predict, and ultimately design, materials to absorb acoustic energy.
Although many of the examples provided above are in the area of acoustic transduction, transducer systems, and clas- sic acoustical materials, several emerging areas of research that have gained significant attention across the acoustics community have relevance to the TCEA. The first is the area of acoustic metamaterials, which has been the subject of special issues of JASA in 2012 and 2016 and featured in
Acoustics Today (Haberman and Norris, 2016). Research- ers in the TCEA have provided fundamental and applied contributions to this research area and are well-suited to help transition fundamental concepts to new technologies.
Another active area of engineering acoustics research is on the development of new electroacoustic transduction materials. This topic spans ongoing research on single crystal relaxor ferroelectric materials and textured piezo- electric ceramics to improve sonar and biomedical imaging systems as well as carbon nanotube and graphene-based thermoacoustic transducers (Mayo, 2018) and bio-inspired sensing mechanisms and signal-processing techniques.
The rapid expansion of voice-interactive consumer elec- tronic devices has prompted researchers in the TCEA and numerous other technical committees to investigate
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