Energetic Noise Research Articles

Quantifying microseismic noise generation from coastal reflection of gravity waves recorded by seafloor DAS

SUMMARY Secondary microseisms are the most energetic noise in continuous seismometer recordings. They are generated by interactions between ocean waves, including between gravity waves incident on and reflected from the coast. Coastal reflections of ocean waves leading to coastal microseismic sources are hard to estimate in various global numerical wave models, and independent quantification of these coastal sources through direct measurements can greatly improve these models. Here, we exploit a 41-km-long submarine optical fibre (OF) cable located offshore Toulon, France, using distributed acoustic sensing (DAS). We record both the amplitude and frequency of seafloor strains induced by ocean surface gravity waves, as well as secondary microseisms caused by the interaction of gravity waves incident and reflected from the coast. By leveraging the spatially distributed nature of DAS measurements, additional fundamental information is recovered such as the velocity and azimuth of the waves. We find that on average 30 per cent of the gravity waves are reflected at the coast generating local sources of secondary microseisms that manifest as Scholte waves. These local sources represent the most energetic contribution to the seismic noise recorded along the OF and by an onshore broad-band station located near the DAS interrogator. Furthermore, we estimate a coastal reflection coefficient of ocean surface gravity waves R2 of about 0.07, which provides improved constraints for seismic noise generation models. In addition, we show that new local sources of microseisms can be generated when gravity waves characteristics (azimuth and frequency content) change and lead to some delays between the OF cable and buoy recordings. These analyses pave the way for a wide use of DAS data to monitor ocean–solid earth interactions as they provide a wealth of information on the reflection of gravity waves, coastal microseismic sources, and new constraints for numerical models of microseismic noise.

Can visual capture of sound separate auditory streams?

In noisy contexts, sound discrimination improves when the auditory sources are separated in space. This phenomenon, named Spatial Release from Masking (SRM), arises from the interaction between the auditory information reaching the ear and spatial attention resources. To examine the relative contribution of these two factors, we exploited an audio-visual illusion in a hearing-in-noise task to create conditions in which the initial stimulation to the ears is held constant, while the perceived separation between speech and masker is changed illusorily (visual capture of sound). In two experiments, we asked participants to identify a string of five digits pronounced by a female voice, embedded in either energetic (Experiment 1) or informational (Experiment 2) noise, before reporting the perceived location of the heard digits. Critically, the distance between target digits and masking noise was manipulated both physically (from 22.5 to 75.0 degrees) and illusorily, by pairing target sounds with visual stimuli either at same (audio-visual congruent) or different positions (15 degrees offset, leftward or rightward: audio-visual incongruent). The proportion of correctly reported digits increased with the physical separation between the target and masker, as expected from SRM. However, despite effective visual capture of sounds, performance was not modulated by illusory changes of target sound position. Our results are compatible with a limited role of central factors in the SRM phenomenon, at least in our experimental setting. Moreover, they add to the controversial literature on the limited effects of audio-visual capture in auditory stream separation.

Effect of competitive acoustic environments on speech intelligibility

Excessive noise and reverberation times degrade listening abilities in everyday life environments. This is particularly true for school settings. Most classrooms in Italy are settled in historical buildings that generate competitive acoustic environments. So far, few studies investigated the effect of real acoustics on speech intelligibility and on the spatial release from masking, focusing more on laboratory conditions. Also, the effect of noise on speech intelligibility was widely investigated considering its energetic rather than its informational content. Therefore, a study involving normal hearing adults was performed presenting listening tests via headphone and considering the competitive real acoustics of two primary-school classrooms with reverberation time of 0.4 s and 3.1 s, respectively. The main objective was the investigation of the effect of reverberation and noise on the spatial release from masking to help the design of learning environments. Binaural room impulse responses were acquired, with noise sources at different azimuths from the listener’s head. The spatial release from masking was significantly affected by noise type and reverberation. Longer reverberation times brought to worst speech intelligibility, with speech recognition thresholds higher by 6 dB on average. Noise with an informational content was detrimental by 7 dB with respect to an energetic noise.

Effects of background noise on the speech acoustics of people with aphasia

We investigated the effect of six background noise conditions (silent baseline, pink noise, monologue, lively conversation, one-sided phone call, and cocktail noise) on acoustic measures of speech during story retells in people with aphasia. Eleven individuals with aphasia and 11 age- and gender-matched control participants heard the background noise through headphones while they retold short stories. We measured mean and standard deviation of intensity and fundamental frequency (F0), and speech rate. A Matlab application computed a speaking time ratio measure (i.e., time speaking versus time pausing). With the exception of the monologue and one-sided phone call condition, both people with aphasia and control participants significantly increased their intensity and F0 in the presence of background noise, regardless of noise type. Additionally, participants with aphasia had significantly lower speaking time ratios and speaking rates than control participants. All speakers made acoustic changes while hearing background noise, likely because speech intensity rises in an effort to increase the signal-to-noise ratio, while mean F0 increases due to a presumed rise in subglottal pressure. Further research is suggested to investigate other acoustic differences, possibly at the segmental level, between speech produced in informational and energetic background noise conditions.

Effect of reverberation and noise type on speech intelligibility in real complex acoustic scenarios

Enhanced speech intelligibility in realistic acoustic scenarios guarantees effective communication. Noise and reverberation degrade speech intelligibility, but the combined effect of reverberation, informational noise and position of target, listener and noise source on speech intelligibility still needs to insights. This work investigates the effect of real complex acoustic scenarios on speech intelligibility for adults. In two primary-school classrooms with reverberation time of 0.4 s and 3.1 s, receivers were located on axis with the target at increasing distances, and noise sources were both co-located and spatially separated from the target at different distances providing various degrees of energetic and informational masking. Noise level was maintained constant and set at 60 dB at the receiver's position, regardless of the noise source distance. The longer reverberation time resulted in worse speech recognition thresholds (SRT80s) by 6 dB on average. The competitive effect of informational noise resulted in increased SRT80s by 7 dB on average, in comparison to energetic noise. The SRT80 increases by ~2 dB with doubling the target-to-receiver distance when the noise source is close to the receiver, accounting for both reverberations and noise types. The spatial release from masking resulted in improved speech intelligibility by up to ~3 dB when the noise source is 1 m far from the receiver for energetic masker for low reverberation and, unexpectedly, for the informational masker in high reverberation. This may indicate that a perceptual segregation mechanism sorts out competing voices of informational masker according to their directions in least favorable listening situations.

Multimeasurement aliased-noise attenuation for sparse land seismic acquisition using compressed sensing

Land data are contaminated by energetic surface waves that have low apparent velocities relative to the seismic signal. The conventional land acquisition approach to noise attenuation is to deploy arrays of hard-wired geophones whose combined response acts as a spatial filter. Besides the shortcomings of a fixed array response that is sensitive to perturbations, using a large amount of equipment limits the field efficiency of array-based acquisition. The advent of point-receiver acquisition technology addresses some of these limitations by enabling measurement of each single geophone along a receiver line and removing the slowest energetic noise by velocity-based filtering. However, according to the classic sampling theorem, the proper sampling of noise requires sampling the shortest wavelength twice. Because surface waves have slow propagation velocities, it is not feasible to sample the noise properly and a compromise is made between quality and efficiency. We have developed two different methods to improve the efficiency of point-receiver technology by allowing for wider receiver spacing without compromising the coherent noise attenuation capabilities. First, we combine compressed sensing-based methods such as the matching pursuit approach with the gradient measurement inferred from a novel 5C sensor to dealias and attenuate source-generated noise. Second, we have developed a method to design optimized acquisition geometries by using the spectral characteristics of the surface waves, where the objective is to place a limited number of receivers at the most favorable locations to help attenuate the coherent noise. We determine the effectiveness of our methods through synthetic and field data examples in which we find that spatially aliased coherent noise can be reconstructed to a denser grid and attenuated.

Hydroacoustic modelling applied in hydraulic components: a test rig based experiment

The exponential increase of computational power has allowed the development of numerical simulation methods. Numerical simulation is widely used in the industries at all stages of the product development process: the design support, comparison between several solutions, final validation. Virtual prototyping and optimization methods enable to meet requirements from the first physical prototype. Hydraulic power transmission, which can be considered as a mature technology providing an unrivalled specific power, is widespread for Off-Road and On-Road vehicles. Nevertheless, this kind of technology has two identified weaknesses which are energetic efficiency and noise generated during the operation. In such a context, the proposed research project focuses on the modelling, the analysis and the simulation for a component set constituting a hydraulic transmission taking into account the flow and pressure ripples. Thus, this work deals with the modelling of fluid borne noise applied to a hydrostatic transmission. From the state-of-the-art on hydroacoustic spread laws, the paper introduces an original method for the modelling of the transition from frequency to temporal domain allowing an analysis of the unsteady behaviour of hydraulic systems. Then, this method is applied to characterize the hydroacoustic behaviour of a rigid pipe using a simulation software. Finally, the used experimental means are presented, as well as a correlation between real measurement and computational analysis applied for a rigid pipe.

Acoustic and pressure characteristics of a ported shroud turbocompressor operating at near surge conditions

The operation of compressor at lower mass flow rates is limited by surge which is marked by large fluctuations in operational variables and accompanied by significant increase in noise. Ported shroud casing treatment is a widely used method to control the flow near unstable conditions in order to obtain a stable operation and enhance deep surge margin. The research on the acoustic effects of the ported shroud design is limited. Therefore, this paper numerically characterises the acoustic features of a turbocharger compressor with ported shroud design operating at marginal or soft surge conditions and investigates the correlation between acoustic characteristics and the spatial flow structures. The acoustic and the flow field features are analysed using spectral signatures obtained from an experimentally validated numerical model using both performance and acoustic measurements. Propagation of the frequency content through the ducts has been estimated with the aid of the beamforming and method of characteristics to enhance the content coming from the compressor. Expected acoustic phenomena such as rotating order tones and blade passing peaks are correctly identified in the modelled spectrum with the limitation to capture the specific broadband features. Hence, the numerical model can be used to further the research encompassing the impact these flow enhancement solutions have on the noise emission of the turbocharger. Inspection of the flow field shows radially exiting fluid at the ported shroud slot leading to the formation of the high-speed jets exiting the ported shroud cavity. Circumferential propagation of the stall cells is also identified in the impeller. Further inspection of the pressure field through modal decomposition implies the localisation of the energetic noise sources in the impeller downstream components. The influence of the ported shroud cavity on the acoustic characteristic of the compressor is not significant and is limited to the propagation of the tonal noise in the direction of impeller upstream.

Low-Frequency Satellite Communication System Technical Means’ Parameters Synthesis by the Requirements for Energetic Concealment and Noise Immunity

The method of technical means parameters synthesis by the requirements for energetic concealment and noise immunity has been developed for satellite communication systems that use reduced (down to 30–100 MHz) carrier frequencies and dual antennae diversity. It allows to calculate the dependence of board transmitter’s emitting power, transmission speeds and transmitted signals’ carrier frequency on the signal reception error probability allowed values, radio link’s energetic reserve and the energetic concealment coefficient.

The impact of different background noises on the Production Effect

The presence of background noise has been previously shown to disrupt cognitive performance, especially memory. The amount of interference is derived from the acoustic characteristics of the noise; energetic vs. informational, steady-state vs. fluctuating. However, the literature is inconsistent concerning the effects of different types of noise on long-term memory free recall. In the present study, we tested the impact of different noises on recall of items that were learned under two conditions – silent or aloud reading, a Production Effect (PE) paradigm. As the PE represents enhanced memory for words read aloud relative to words read silently during study, we focused on the effect of noise on this robust memory phenomenon. The results showed that (a) steady-state energetic noise did not affect memory, with a recall advantage for aloud words (PE), comparable to a no-noise condition, (b) fluctuating-energetic noise and fluctuating-informational (eight-talkers babble) noise eliminated the PE, with similar recall for aloud and silent items. These results are discussed in light of their theoretical implications, stressing the role of attention in the PE. Ecological implications regarding studying in noisy environments are suggested.

Modeling Ultrafast Exciton Migration within the Electron Donor Domains of Bulk Heterojunction Organic Photovoltaics

Recent experimental studies revealed that charge carriers harvested by bulk heterojunction organic photovoltaics can be collected on ultrafast time scales. To investigate ultrafast exciton mobility, we construct simple, nonatomistic models of a common polymeric electron donor material. We first explore the relationship between the magnitude of energetic noise in the model Hamiltonian and the spatial extent of resulting eigenstates. We then employ a quantum master equation approach to simulate migration of chromophore-localized initial excited states. Excitons initially localized on a single chromophore at the center of the model delocalize down polymer chains and across pi-stacked chromophores through a coherent, wavelike mechanism during the first few tens of femtoseconds. We explore the dependence of this coherent delocalization on coupling strength and on the magnitude of energetic noise. At longer times we observe continued migration toward a uniform population distribution that proceeds through an incoherent, diffusive mechanism. A series of simulations modeling exciton harvesting in domains of varying size demonstrates that smaller domains enhance ultrafast exciton harvesting yield. Our nonatomistic model falls short of quantitative accuracy but demonstrates that excitons are mobile within electron donor domains on ultrafast time scales and that coherent exciton transport can enhance ultrafast exciton harvesting.

Speech Discrimination Difficulties in High-Functioning Autism Spectrum Disorder Are Likely Independent of Auditory Hypersensitivity.

Autism Spectrum Disorder (ASD), characterized by impaired communication skills and repetitive behaviors, can also result in differences in sensory perception. Individuals with ASD often perform normally in simple auditory tasks but poorly compared to typically developed (TD) individuals on complex auditory tasks like discriminating speech from complex background noise. A common trait of individuals with ASD is hypersensitivity to auditory stimulation. No studies to our knowledge consider whether hypersensitivity to sounds is related to differences in speech-in-noise discrimination. We provide novel evidence that individuals with high-functioning ASD show poor performance compared to TD individuals in a speech-in-noise discrimination task with an attentionally demanding background noise, but not in a purely energetic noise. Further, we demonstrate in our small sample that speech-hypersensitivity does not appear to predict performance in the speech-in-noise task. The findings support the argument that an attentional deficit, rather than a perceptual deficit, affects the ability of individuals with ASD to discriminate speech from background noise. Finally, we piloted a novel questionnaire that measures difficulty hearing in noisy environments, and sensitivity to non-verbal and verbal sounds. Psychometric analysis using 128 TD participants provided novel evidence for a difference in sensitivity to non-verbal and verbal sounds, and these findings were reinforced by participants with ASD who also completed the questionnaire. The study was limited by a small and high-functioning sample of participants with ASD. Future work could test larger sample sizes and include lower-functioning ASD participants.

Editorial: Using Noise to Characterize Vision.

Editorial: Using Noise to Characterize Vision.

The enhancement of cosmic radio noise absorption due to hiss‐driven energetic electron precipitation during substorms

AbstractThe Van Allen probes, low‐altitude NOAA satellite, MetOp satellite, and riometer are used to analyze variations of precipitating energetic electron fluxes and cosmic radio noise absorption (CNA) driven by plasmaspheric hiss with respect to geomagnetic activities. The hiss‐driven energetic electron precipitations (at L ~ 4.7–5.3, magnetic local time (MLT) ~ 8–9) are observed during geomagnetic quiet condition and substorms, respectively. We find that the CNA detected by riometers increased very little in the hiss‐driven event during quiet condition on 6 September 2012. The hiss‐driven enhancement of riometer was still little during the first substorm on 30 September 2012. However, the absorption detected by the riometer largely increased, while the energies of the injected electrons became higher during the second substorm on 30 September 2012. The enhancement of CNA (ΔCNA) observed by the riometer and calculated with precipitating energetic electrons is in agreement during the second substorm, implying that the precipitating energetic electrons increase CNA to an obviously detectable level of the riometer during the second substorm on 30 September 2012. The conclusion is consistent with Rodger et al. (2012), which suggest that the higher level of ΔCNA prefers to occur in the substorms, because substorms may produce more intense energetic electron precipitation associated with electron injection. Furthermore, the combination of the observations and theory calculations also suggests that higher‐energy electron (>55 keV) precipitation contributes more to the ΔCNA than the lower energy electron precipitation. In this paper, the higher‐energy electron precipitation is related to lower frequency hiss.

Human response to simulated airport noise scenarios in home-like environments

This research is part of a FP7 project supported by the European Commission called “Community oriented solutions to minimize aircraft noise annoyance” (COSMA). The present paper focuses on the development and the application of a methodology for the assessment of changes in airport noise exposure in home-like environments, particularly the design of sound scenarios and of experiments. Two airport noise changes are assessed and compared to a reference scenario: a halving of the number of aircraft, and an improvement in aircraft sound quality. For that purpose, sound perception, annoyance and activity disturbance as well as performances to cognitive tasks (Stroop and Word list Memory) are considered in the experiments involving 142 participants in 3 laboratories. Despite a similar LAeq, overall annoyance significantly decreases when reducing the number of aircraft, which reinforces the interest in a noise event index (NNE-NA) in addition to energetic noise indices for regulatory purposes. Results to a change in aircraft sound quality are largely inconclusive. Further work should address the human response to future airport noise scenarios based on new aircraft designs, including innovative concepts.

Improved Reweighting of Accelerated Molecular Dynamics Simulations for Free Energy Calculation

Accelerated molecular dynamics (aMD) simulations greatly improve the efficiency of conventional molecular dynamics (cMD) for sampling biomolecular conformations, but they require proper reweighting for free energy calculation. In this work, we systematically compare the accuracy of different reweighting algorithms including the exponential average, Maclaurin series, and cumulant expansion on three model systems: alanine dipeptide, chignolin, and Trp-cage. Exponential average reweighting can recover the original free energy profiles easily only when the distribution of the boost potential is narrow (e.g., the range ≤20kBT) as found in dihedral-boost aMD simulation of alanine dipeptide. In dual-boost aMD simulations of the studied systems, exponential average generally leads to high energetic fluctuations, largely due to the fact that the Boltzmann reweighting factors are dominated by a very few high boost potential frames. In comparison, reweighting based on Maclaurin series expansion (equivalent to cumulant expansion on the first order) greatly suppresses the energetic noise but often gives incorrect energy minimum positions and significant errors at the energy barriers (∼2–3kBT). Finally, reweighting using cumulant expansion to the second order is able to recover the most accurate free energy profiles within statistical errors of ∼kBT, particularly when the distribution of the boost potential exhibits low anharmonicity (i.e., near-Gaussian distribution), and should be of wide applicability. A toolkit of Python scripts for aMD reweighting “PyReweighting” is distributed free of charge at http://mccammon.ucsd.edu/computing/amdReweighting/.

Zero-multipole summation method for efficiently estimating electrostatic interactions in molecular system

The zero-multipole summation method has been developed to efficiently evaluate the electrostatic Coulombic interactions of a point charge system. This summation prevents the electrically non-neutral multipole states that may artificially be generated by a simple cutoff truncation, which often causes large amounts of energetic noise and significant artifacts. The resulting energy function is represented by a constant term plus a simple pairwise summation, using a damped or undamped Coulombic pair potential function along with a polynomial of the distance between each particle pair. Thus, the implementation is straightforward and enables facile applications to high-performance computations. Any higher-order multipole moment can be taken into account in the neutrality principle, and it only affects the degree and coefficients of the polynomial and the constant term. The lowest and second moments correspond respectively to the Wolf zero-charge scheme and the zero-dipole summation scheme, which was previously proposed. Relationships with other non-Ewald methods are discussed, to validate the current method in their contexts. Good numerical efficiencies were easily obtained in the evaluation of Madelung constants of sodium chloride and cesium chloride crystals.

The Filtering of the Energetic Particle Noise Captured by the Geostationary Lightning Image Sensor

The Filtering of the Energetic Particle Noise Captured by the Geostationary Lightning Image Sensor

Effects of dialect variation on the semantic predictability benefit

Words in semantically predictable sentences are more intelligible than words in less predictable or semantically anomalous sentences. However, the intelligibility benefit of semantically predictable words is reduced in noise and for non-native listeners, suggesting that semantic context contributes less to intelligibility under difficult listening conditions. The goal of the current study was to explore the effect of dialect variation on the semantic predictability benefit. Larger semantic predictability benefits were observed for more familiar dialects than less familiar dialects. In addition, more dialect differences in the size of the semantic predictability benefit were observed in conditions in which perceptual normalisation was more difficult. These results are consistent with a cue-weighting model in which dialect variation is comparable to energetic noise masking. Listeners attend less to semantic cues when perceptual normalisation for dialect variation is difficult and more to semantic cues when perceptual normalisation is easy.

Zero-Dipole Summation Method for Precisely Estimating Electrostatic Interactions in Molecular Simulation

For computational studies of materials in a realistic manner, appropriate treatment of the Coulombic interaction is critical. Since the potential function is long-range and has both positive and negative signatures, it is not simple to handle the interaction in an effective manner, i.e., with high accuracy, low computational cost, freedom from artifacts, and ease of implementation. We introduce a novel idea, zero-dipole summation, for evaluating the electrostatic energy of classical particle system. The summation prevents the nonzero-charge and nonzero-dipole states artificially generated by simple cutoff truncation, which causes energetic noise and several artifacts. The currently derived energy formula nevertheless takes a simple pairwise form, which utilizes the cutoff procedure but employs a pairwise function changed from the pure Coulomb formula into a new formula taking account of the neutrality of charges and dipoles in the cutoff sphere (Fukuda et al. (2011) J. Chem. Phys. 134, 164107). This simple pairwise form enables us to effectively apply the scheme to high-performance computation. We discuss the theoretical details of our method and investigate the accuracy, stability, and static and dielectric properties of molecular systems via molecular dynamics simulation. We obtained the electrostatic energy error to be 0.01% at practical cutoff distance for an ionic system and a water system. We estimated the radial distribution function and the distant dependent Kirkwood factor for the water system, and confirmed the agreement with those by the Ewald method. Since the Kirkwood factor is very sensitive to the treatment of the electrostatic interaction, the agreement suggests that our method should be distinguishable from many other cutoff-like methods, which often cause the significant disagreement. Accurate electrostatic energies were also calculated with our method for a membrane protein with explicit ions and membrane and water molecules.