<div class="section abstract"><div class="htmlview paragraph">Automotive exhaust noise is one of the major sources of noise pollution and it is controlled by passive control system (mufflers) and active control system (loudspeakers and active control algorithm). Mufflers are heavy, bulky and large in size while loudspeakers have a working temperature limitation. Carbon nanotube (CNT) speakers generate sound due to the thermoacoustic effect. CNT speakers are also lightweight, flexible, have acoustic and light transparency as well as high operating temperature. These properties make them ideal to overcome the limitations of the current exhaust noise control systems. An enclosed, coaxial CNT speaker is designed for exhaust noise cancellation application. The development of a 3D multi-physics (coupling of electrical, thermal and acoustical domains) model, for the coaxial speaker is discussed in this paper. The model is used to simulate the sound pressure level, input power versus ambient temperature and efficiency. The 3D model provides accurate results of the temperature profile and heat flow as compared to a 2D model. Also, the flow of exhaust gases can be efficiently modeled using a 3D model. The flow analysis would help understand any flow penetration into the speaker as well as the effect of heat transfer due to the flow. The model is validated by comparing the experimental results with the simulation results. Along with multi-physics simulation, CFD analysis of the coaxial speaker is also studied in this paper. The CFD analysis is focused on the backpressure generated by the speaker and the flow path of the exhaust gases inside the CNT speaker.</div></div>

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Prey fish abundances in the Great Lakes are a driver for several agencies commitments to the Council of Lake Committees to support fisheries management. These management decisions have profound economic and social impacts within the Great Lakes region. Fisheries estimates done by echosounders or trawling may be biased due to the propagated noise from large fisheries vessels. In the first year of a four year collaborative study, crewed fisheries vessels and uncrewed Saildrone vessels were used to compare abundance estimates between “loud” and “quiet” vessels. In order to quantify the effects of ship noise on prey fish abundance estimates, a mobile ship noise measurement system was designed and deployed to measure radiated acoustic signatures of several ships in the Great Lakes. This talk will discuss the deployment of a mobile underwater acoustic test range, and show initial results of ship noise measurements from the first year of the program. In addition, an overview of the echosounder abundance results will be given along with plans for future data generation, analysis, and comparison between crewed and autonomous systems.

The accumulation of ice on helicopter blades imposes limitations on the design and operation of rotorcrafts due to the large power requirement of thermal heating mats. Carbon nanotube (CNT) loudspeakers present a lightweight and efficient solution to this issue, utilizing both thermal and vibratory methods to remove ice and prevent it from forming. To evaluate the deicing capabilities of CNT, an enclosure was created to encapsulate the loudspeaker between two thin layers of aluminum to simulate the rotor blade surface. The speaker was then operated at a range of amplitudes and frequencies in simulated cold weather conditions. Preliminary tests show promising results, with surface temperatures exceeding 120°C in under four minutes when operated in a −20°C environment and surface excitation resultant from the ultrasonic vibration. Although further testing is needed, CNT loudspeakers show great promise in becoming a lightweight and efficient solution to the issue of ice accumulation on the surface of rotor blades.

Acoustic surveys of fish are a foundational component of many fisheries monitoring programs, including surveys in the Great Lakes. These surveys are conducted with traditional crewed and motorized vessels, but fish avoidance of these types of platforms has been reported in multiple studies, potentially biasing estimates. A quiet uncrewed surface vessel, Saildrone, was equipped with a 120 kHz Simrad EK80 transducer and deployed in Lakes Huron, Michigan, and Superior in the summers of 2021 and 2022. The drone was then overtaken by numerous motorized vessels using transducers with the same frequency. The average target depth, target strength, and nautical area scattering during overtakes were compared. We looked for a fish behavioral response with General Additive Models using distance from the Saildrone to the vessel as the predictor. We also compared the effectiveness of acoustic surveys from each platform with analyses of variances over 2 km sections of the overtake. Fish showed a limited response to approaching vessels, and acoustic estimates of fisheries relevant measures were similar between Saildrone and motorized vessels. Findings from this work will inform interpretation of acoustic data in the Great Lakes and provide the largest scale testing of fish avoidance to acoustic surveys to date.