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1. One year of sound recorded by a MERMAID float in the Pacific: hydroacoustic earthquake signals and infrasonic ambient noise

   https://doi.org/10.1093/gji/ggab296  

   Pipatprathanporn, Sirawich; Simons, Frederik J (September 2021, Geophysical Journal International)

   SUMMARY A fleet of autonomously drifting profiling floats equipped with hydrophones, known by their acronym mermaid, monitors worldwide seismic activity from inside the oceans. The instruments are programmed to detect and transmit acoustic pressure conversions from teleseismic P wave arrivals for use in mantle tomography. Reporting seismograms in near-real time, within hours or days after they were recorded, the instruments are not usually recovered, but if and when they are, their memory buffers can be read out. We present a unique 1-yr-long data set of sound recorded at frequencies between 0.1 and 20 Hz in the South Pacific around French Polynesia by a mermaid float that was, in fact, recovered. Using time-domain, frequency-domain and time-frequency-domain techniques to comb through the time-series, we identified signals from 213 global earthquakes known to published catalogues, with magnitudes 4.6–8.0, and at epicentral distances between 24° and 168°. The observed signals contain seismoacoustic conversions of compressional and shear waves travelling through crust, mantle and core, including P, S, Pdif, Sdif, PKIKP, SKIKS, surface waves and hydroacoustic T phases. Only 10 earthquake records had been automatically reported by the instrument—the others were deemed low-priority by the onboard processing algorithm. After removing all seismic signals from the record, and also those from other transient, dominantly non-seismic, sources, we are left with the infrasonic ambient noise field recorded at 1500 m depth. We relate the temporally varying noise spectral density to a time-resolved ocean-wave model, WAVEWATCH III. The noise record is extremely well explained, both in spectral shape and in temporal variability, by the interaction of oceanic surface gravity waves. These produce secondary microseisms at acoustic frequencies between 0.1 and 1 Hz according to the well-known frequency-doubling mechanism. 

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2. Bottom pressures in a shallow compressible ocean due to nonlinear wave–non-uniform elastic-seafloor interactions

   https://doi.org/10.1017/jfm.2026.11421  

   Korde, Umesh A; Elgar, S (April 2026, Journal of Fluid Mechanics)

   The generation and propagation of acoustic-gravity–Scholte wave fields produced by different types of nonlinear interactions between ocean surface waves and shallow, non-uniform depth contours of an elastic seafloor are investigated. Specifically, nonlinear interactions between surface waves and the seafloor, surfacewaves themselves and the seafloor, and acoustic-gravity-waves and the seafloor are shown to produce resonantly strong bottom pressures. Whereas the interaction between shoreward-propagating surface waves and seafloor depth contours (and the resulting seafloor waves and microseisms) has been discussed in the literature, not much is known about the compression wave–seafloor wave groups forming an important component of the overall energy transfer process in shallow water. Forcing due to the different wave interactions involving the seafloor depth contours and the dispersion relations for the coupled ocean–seafloor system are derived, providing estimates of the energy transfer that results at resonance when the interaction produces a wavenumber–frequency combination that lies on one of the dispersion surfaces for the two-media system. Wavenumber spectra and their temporal evolution are found analytically for stationary random surface-wave fields, and the acoustic-gravity wave potentials, seafloor pressure amplitudes, seafloor power densities and Scholte wave amplitudes are computed, and their sensitivity to critical parameters is estimated. The nonlinear interactions derived here may account for some of the 200 % increase of low-frequency ($$0.01\leqslant f\leqslant 0.03$$Hz) spectral densities of bottom pressure observed between 25 and 8 m water depths in the Atlantic Ocean at a site off Duck, NC. Further, subject to experimental validation, the power densities estimated here could contribute energy for sensing operations. 

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3. The Influence of Atmospheric Bores on Nocturnal Convection Initiation in Weakly Forced Synoptic Environments

   https://doi.org/10.1175/MWR-D-23-0080.1  

   Reif, Dylan W; Bluestein, Howard B; Parsons, David B (July 2024, Monthly Weather Review)

   McTaggart-Cowan, R (Ed.)

   Abstract This study creates a composite sounding for nocturnal convection initiation (CI) events under weakly forced conditions and utilizes an idealized numerical simulation to assess the impact of atmospheric bores on these environments. Thirteen soundings were used to create this composite sounding. Common conditions associated with these weakly forced environments include a nocturnal low-level jet and a Brunt–Väisälä frequency of 0.011 s⁻¹above 900 hPa. The median lift needed for parcels to realize any convective instability is 490 m, the median convective available potential energy of these convectively unstable parcels is 992 J kg⁻¹, and the median initial pressure of these parcels is 800 hPa. An idealized numerical simulation was utilized to examine the potential influence of bores on CI in an environment based on composite sounding. The characteristics of the simulated bore were representative of observed bores. The vertical velocities associated with this simulated bore were between 1 and 2 m s⁻¹, and the net upward displacement of parcels was between 400 and 650 m. The vertical displacement of air parcels has two notable phases: lift by the bore itself and smaller-scale lift that occurs 100–150 km ahead of the bore passage. The prebore lift is between 50 and 200 m and appears to be related to low-frequency waves ahead of the bores. The lift with these waves was maximized in the low to midtroposphere between 1 and 4 km AGL, and this lift may play a role in assisting CI in these otherwise weakly forced environments. 

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4. VoiceFormer: Fusing Non-Acoustic Motion Sensors for High-Fidelity Voice Synthesis in Mobile Devices

   https://doi.org/10.1145/3779062  

   Yan, Xiaokai; Liang, Yunji; Liu, Lei; Samtani, Sagar; Guo, Bin; Yu, Zhiwen (February 2026, ACM Transactions on Privacy and Security)

   With the popularity of mobile devices, a variety of motion sensors are integrated to enhance the user experience. Although existing studies demonstrated that non-acoustic motion sensors can be attacked by adversaries, they overlook the limited sampling frequencies of motion sensors (e.g., < 500 Hz) in mobile devices and are evaluated in the controlled laboratory settings. In this article, we explore a new attack model on non-acoustic motion sensors based on the off-the-shelf mobile devices. We propose a general framework namedVoiceFormerto synthesize high-fidelity speeches based on the vibrations of accelerometers and gyroscopes with a low sampling frequency. Specifically, inVoiceFormer, we introduce a signal alignment approach to remove the time offsets between two nonsynchronous signals, and leverage Time Interleaved Analog-Digital-Conversion (TI-ADC) to generate a high-frequency synthetic signal (e.g., > 8 KHz) based on the vibration signals of accelerometers and gyroscopes on the same motherboard. To synthesize the high-fidelity acoustic waveforms, we propose a wavelet-based generative adversarial network to learn the spatiotemporal latent mapping between vibrations and original speech signals. Extensive experimental results demonstrate the feasibility of voice synthesis by spying the low-frequency non-acoustic motion sensors in off-the-shelf mobile devices.VoiceFormershows impressive performance in the synthesized acoustical signals with a Mean Opinion Score of 3.38. Although there are significant differences of mobile devices in hardware settings, VoiceFormer shows robust performance in synthesizing intelligible voice signals. Our results suggest that eavesdropping an off-the-shelf mobile device remotely by fusing non-acoustic sensors is feasible. 

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5. Implementation of Sub‐Grid Scale Temperature Perturbations Induced by Non‐Orographic Gravity Waves in WACCM6

   https://doi.org/10.1029/2024MS004625  

   Yook, Simchan; Solomon, Susan; Weimer, Michael; Kinnison, Douglas E; Garcia, Rolando; Stone, Kane (April 2025, Journal of Advances in Modeling Earth Systems)

   Abstract Atmospheric gravity waves can play a significant role on atmospheric chemistry through temperature fluctuations. A recent modeling study introduced a method to implement subgrid‐scaleorographicgravity‐wave‐induced temperature perturbations in the Whole Atmosphere Community Climate Model (WACCM). The model with a wave‐induced temperature parameterization was able to reproduce for example, the influence of mountain wave events on atmospheric chemistry, as highlighted in previous literature. Here we extend the subgrid‐scale wave‐induced temperature parameterization to also includenon‐orographicgravity waves arising from frontal activity and convection. We explore the impact of these waves on middle atmosphere chemistry, particularly focusing on reactions that are strongly sensitive to temperature. The non‐orographic gravity waves increase the variability of chemical reaction rates, especially in the lower mesosphere. As an example, we show that this, in turn, leads to increases in the daytime ozone variability. To demonstrate another impact, we briefly investigate the role of non‐orographic gravity waves in cirrus cloud formation in this model. Consistent with findings from the previous study focusing on orographic gravity waves, non‐orographic waves also enhance homogeneous nucleation and increase cirrus clouds. The updated method used enables the global chemistry‐climate model to account for both orographic and non‐orographic gravity‐wave‐induced subgrid‐scale dynamical perturbations in a consistent manner. 

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