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The generalized leaky filtered-x least mean square (GLFxLMS) algorithm can reduce the noise amplification caused by the waterbed effect in feedback active control systems effectively; however, it suffers from a high computation complexity. Hence, a frequency band constrained filtered-x least mean square algorithm is proposed to reduce the computation complexity of the GLFxLMS algorithm by replacing the penalty term containing a symmetric Toeplitz matrix in the cost function with the mean square of a penalty signal. The simulation results based on the measured transfer functions of an active headrest system show that the proposed algorithm has the same performance as the GLFxLMS algorithm, but with much lower computation complexity.Acoustic scattering from layered seafloors exhibits dependence on both the mean geoacoustic layering, as well as the roughness properties of each layer. Several theoretical treatments of this environment exist, including the small roughness perturbation approximation, the Kirchhoff approximation, and three different versions of the small slope approximation. All of these models give different results for the scattering cross section and coherent reflection coefficient, and there is currently no way to distinguish which model is the most correct. In this work, an integral equation for scattering from a layered seafloor with rough interfaces is presented, and compared with small roughness perturbation method, and two of the small slope approximations. It is found that the most recent small slope approximation by Jackson and Olson [J. Acoust. Soc. Am. 147(1), 56-73 (2020)] is the most accurate when the root-mean-square (rms) roughness is large, and some models are in close agreement with each other when the rms roughness is small.Conventional reverberation reduction methods are conducted with single-ping data and may fail in a low signal-to-reverberation ratio (SRR) environment. To improve the performance of reverberation reduction, multi-ping data are fully considered in this paper. The reverberation can be treated as a combination of the steady component of reverberation and reverberation fluctuations, and then an alternating direction multiplier method is proposed to reduce the steady component of the reverberation. By exploiting the evolution of the target location along multiple pings, the reverberation fluctuation is reduced by the probabilistic data association method. The proposed method was verified by the field data, and the results show that compared with the accelerated proximal gradient method, the sparse coefficient is improved by a factor of 1.23, and the signal excess is improved by an average value of 2.0 dB. In addition, the performance of the proposed method is found to be closely related to the signal-to-reverberation-fluctuation ratio rather than only the SRR.High-altitude monitoring of low-frequency acoustic waves (infrasound) on Earth has regained prominence in recent years, primarily driven by improvements in light-weight sensor technology and advances in scientific ballooning techniques. Balloon-borne infrasound monitoring is also being proposed as a remote sensing technique for planetary exploration. Contrary to ground-based infrasound monitoring, the infrasound noise background in the stratosphere as measured by a balloon remains uncharacterized and the efficacy of wind noise mitigation filters has not been investigated. In this study, an analysis of pressure data collected using infrasound microbarometers during the flight of a long-duration zero pressure balloon is presented. A dramatic reduction of background noise in the stratosphere is demonstrated and it is shown that wind noise mitigation filters are not effective at reducing wind noise under these conditions. Results from this study demonstrate stratospheric balloons as a low-noise platform for infrasound monitoring and motivate the development of improved noise mitigation tools.Impulse response (IR) measurement methods with deterministic signals have been used in various fields of acoustics for decades, yet there is still a hesitancy to apply them by some practitioners, especially in the building acoustics community. This hesitancy is also the topic of discussion in ASTM standards committees because IR methods are not allowed in ASTM standards. The criticism that prevents a more widespread adoption is that the description of IR methods in existing standards such as ISO 18233 is not sufficient to enable practitioners and equipment manufacturers to reliably implement them. Previous publications have described the theoretical background well, but they have not given sufficient guidance for the practical application with respect to the parameters of the measurement signal. To provide more guidance and show the practical advantages of IR measurement methods, this paper investigates the effects of the design parameters of swept-sine signals. Measurements in a reverberant chamber are used to highlight potential problems and appropriate solutions derived from a theoretical background. Suggestions for the design of measurement signals and for the post-processing of the measured data are provided to achieve optimal and reliable results. This contribution hopefully gives practitioners more confidence in applying the method in the future.With the increased availability of highly maneuverable unmanned surface/underwater vehicles, abundant ocean data can now be collected. This study uses tomographic techniques to extend the survey area covered by moving vehicles. An acoustic reciprocal transmission experiment was conducted using three tomographic sensors installed on an autonomous underwater vehicle, a fishing ship, and a buoy. The distributed sensing method is applied for currents estimation. The estimated currents near the ship show consistent results with the direct measurements. In particular, an anticyclonic circulation was revealed. selleck kinase inhibitor Further, a general least-squares method is employed to improve the estimate of this vortical structure.A cellular stimulation device with a pressurized chamber is developed to investigate the effect of ultrasound and pressure fluctuation on nucleus pulposus (NP) cells. The pressurized chamber is designed to emulate the in vivo environment of intervertebral discs, which are under dynamic pressure, and to emulate impact during sports and exercise. Both hydrostatic pressure and ultrasound stimulation increase phosphorylation of ERK (pERK) in NP cells, and promote its translocation into nucleus. This increase in pERK levels might be activated through calcium signaling pathways as intracellular calcium in NP cells was strongly elevated by pressure changes.