Sound Fluctuations Research Articles

Generation of 1/<i>f</i><sup>α</sup>-like amplitude and period fluctuations in complex sounds based on the additive synthesis approach

Generation of 1/<i>f</i><sup>α</sup>-like amplitude and period fluctuations in complex sounds based on the additive synthesis approach

Sound intensity fluctuations caused by internal solitary wave train in the South China Sea

Dynamic internal solitary wave (ISW) can cause significant underwater sound fluctuations. In this paper, the periodic characteristics of sound intensity fluctuations and related physical mechanisms are investigated in the scenario that an ISW train passing through the acoustic path from source to receivers. From simulation results and experimental data, it is shown that the sound intensity fluctuates quasi-periodically, and the predominant fluctuation frequency is associated with modal interference and modal intensity. The initial mode coefficients at the source and the mode coupling are responsible for the fluctuations of modal intensities, and one of the predominant fluctuation periods is the same as that of the ISWs.

Issues in mid-frequency sound intensity fluctuation on the Washington Shelf

Strong mid-frequency sound intensity fluctuations were found on the Washington shelf during an experiment in the summer of 2022. The Scintillation Index (SI) of integrated sound energy on single channels at 20 km range was near unity for both 3.5 kHz and 6.0 kHz signals. Accompanying oceanographic measurements from moorings and a towed profiling system revealed sound field variability at multiple time and spatial scales caused by linear and nonlinear internal waves, internal tides, and coastal trapped waves. While the 2022 dataset provides valuable information for addressing issues on intensity fluctuation, additional experimental data are needed to understand the impacts on active and passive mid-frequency sonar systems. To that end, a second Washington Shelf experiment is being planned for the summer of 2025. This talk will discuss the planned measurements and the range of issues to be addressed. These include the frequency-dependence of SI over 1–10 kHz, broadband fading, vertical and horizontal coherence, and the impacts of variability on propagation in subsurface ducts. These measurements are important for investigating fundamental oceanographic causes of sound fluctuation as well as for the design of appropriate signal processing methods. (Work supported by the Office of Naval Research.)

Detection of Rain in Tropical Cyclones by Underwater Ambient Sound

Abstract Rain in tropical cyclones is studied using eight time series of underwater ambient sound at 40–50 kHz with wind speeds up to 45 m s−1 beneath three tropical cyclones. At tropical cyclone wind speeds, rain- and wind-generated sound levels are comparable, and therefore rain cannot be detected by sound level alone. A rain detection algorithm that is based on the variations of 5–30-kHz sound levels with periods longer than 20 s and shorter than 30 min is proposed. Faster fluctuations (<20 s) are primarily due to wave breaking, and slower ones (>30 min) are due to overall wind variations. Higher-frequency sound (>30 kHz) is strongly attenuated by bubble clouds. This approach is supported by observations that, for wind speeds < 40 m s−1, the variation in sound level is much larger than that expected from observed wind variations and is roughly comparable to that expected from rain variations. The hydrophone results are consistent with rain estimates by the Tropical Rainfall Measuring Mission (TRMM) satellite and with Stepped-Frequency Microwave Radiometer (SFMR) and radar estimates by surveillance flights. The observations indicate that the rain-generated sound fluctuations have broadband acoustic spectra centered around 10 kHz. Acoustically detected rain events usually last for a few minutes. The data used in this study are insufficient to produce useful estimation of rain rate from ambient sound because of limited quantity and accuracy of the validation data. The frequency dependence of sound variations suggests that quantitative rainfall algorithms from ambient sound may be developed using multiple sound frequencies. Significance Statement Rain is an indispensable process in forecasting the intensity and path of tropical cyclones. However, its role in the air–sea interaction is still poorly understood, and its parameterization in numerical models is still in development. In this work, we analyzed sound measurements made by hydrophones on board Lagrangian floats beneath tropical cyclones. We find that wind, rain, and breaking waves each have distinctive signatures in underwater ambient sound. We suggest that the air–sea dynamic processes in tropical cyclones can be explored by listening to ambient sound using hydrophones beneath the sea surface.

Analysis of Sound Fluctuations in Shallow Water in High Sea States

Sound intensity fluctuation plays a significant role in underwater acoustic studies. In this article, an experiment was conducted in the South China Sea using a buoy system that autonomously emitted and received sound signals to obtain data on sound fluctuations under different wind conditions (in windy weather) for about 179 h. Results showed that the fluctuation of the transmission loss in a fixed position reached up to 15–20 dB. Different potential reasons for this transmission loss fluctuation are analyzed. Using the wind speed data provided by the Earth system, the sea surface wave spectrum model, and the bubble layer model, the fluctuation of the transmission loss was simulated based on the modified Ramsurf sound propagation model. The simulation and experimental results were in good agreement with each other. Therefore, the fluctuation of the transmission loss due to wind-generated waves in high sea states should be considered while studying underwater communication, particularly in shallow water with a positive gradient sound velocity profile.

Speech Categorization Reveals the Role of Early-Stage Temporal-Coherence Processing in Auditory Scene Analysis.

Temporal coherence of sound fluctuations across spectral channels is thought to aid auditory grouping and scene segregation. Although prior studies on the neural bases of temporal-coherence processing focused mostly on cortical contributions, neurophysiological evidence suggests that temporal-coherence-based scene analysis may start as early as the cochlear nucleus (i.e., the first auditory region supporting cross-channel processing over a wide frequency range). Accordingly, we hypothesized that aspects of temporal-coherence processing that could be realized in early auditory areas may shape speech understanding in noise. We then explored whether physiologically plausible computational models could account for results from a behavioral experiment that measured consonant categorization in different masking conditions. We tested whether within-channel masking of target-speech modulations predicted consonant confusions across the different conditions and whether predictions were improved by adding across-channel temporal-coherence processing mirroring the computations known to exist in the cochlear nucleus. Consonant confusions provide a rich characterization of error patterns in speech categorization, and are thus crucial for rigorously testing models of speech perception; however, to the best of our knowledge, they have not been used in prior studies of scene analysis. We find that within-channel modulation masking can reasonably account for category confusions, but that it fails when temporal fine structure cues are unavailable. However, the addition of across-channel temporal-coherence processing significantly improves confusion predictions across all tested conditions. Our results suggest that temporal-coherence processing strongly shapes speech understanding in noise and that physiological computations that exist early along the auditory pathway may contribute to this process.SIGNIFICANCE STATEMENT Temporal coherence of sound fluctuations across distinct frequency channels is thought to be important for auditory scene analysis. Prior studies on the neural bases of temporal-coherence processing focused mostly on cortical contributions, and it was unknown whether speech understanding in noise may be shaped by across-channel processing that exists in earlier auditory areas. Using physiologically plausible computational modeling to predict consonant confusions across different listening conditions, we find that across-channel temporal coherence contributes significantly to scene analysis and speech perception and that such processing may arise in the auditory pathway as early as the brainstem. By virtue of providing a richer characterization of error patterns not obtainable with just intelligibility scores, consonant confusions yield unique insight into scene analysis mechanisms.

Prediction of sound pressure fluctuations in the start-up phase of thermoacoustic oscillations under external perturbation

Prediction of sound pressure fluctuations in the start-up phase of thermoacoustic oscillations under external perturbation

Sound in occupied open-plan offices: Objective metrics with a review of historical perspectives

Open-plan offices (OPOs) have been around for more than half a century now, chronicling the vicissitudes of workplace topography amongst other factors. This paper addresses one such factor – the sound environment in occupied OPOs in relation to several objective workplace parameters, using measurements in contemporary OPOs and comparisons with studies over the last 50 years. Omnidirectional and binaural sound measurements were conducted in 43 offices during typical working hours. The results describe variation in several acoustic and psychoacoustic metrics, and present statistical models that predict these metrics as a function of the number of workstations in offices. LA,eq of 53.6 dB is typical for occupied OPOs, with spectral slope of approximately −4 dB/octave. LA,eq values do not vary much over the workplace parameters studied (e.g., floor plate area, work activity, etc), except for −2.7 dB and −4.1 dB differences between offices with/without carpeting, and offices with ceiling absorption but with/without carpeting, respectively; most likely from reduced floor impact noise leading to speech level reduction. Sound fluctuation, as characterised by the metric Noise Climate (NCl: LA10 – LA90) and the psychoacoustic Fluctuation Strength (FS), decreases significantly with increasing number of workstations in OPOs. This suggests lesser auditory distraction in larger offices, which needs further investigation. In terms of historical trends, OPOs have become quieter over the years, especially background noise quantified as LA90, although there are several subtleties. Overall, current findings can inform several OPO design perspectives including policy documents, provide values for laboratory simulations of OPO acoustic environments, help interpret subjective impressions of OPO occupants, etc.

Keragaman Suara Tonggeret dan Jangkrik di Taman Nasional Gunung Gede Pangrango

Indonesia is a biodiversity country and has much of samples of bioacoustics but there are no bioacoustics data collected and saved to be referred. Bioacoustics is a study of frequency range, sound amplitudo intensity, sound fluctuation, and sound patterns. It is very useful to study more about population presumption and species determination. This insect bioacoustics research is done at Gunung Gede Pangrango National Park and aims to analyse variety of sound frequency of cicada and cricket. Methods which are used are recording the sounds, editing and analyzing the record result with Praat and Raven Lite 2.0 softwares, and analysing the environment. Analysing the sounds which is done is to find miximum frequency, minimum frequency, and average frequency. The result of the sounds analysis is compared to database in Singing Insect of North America (SINA). Environmental analysing includes temperature, air humidity, and light intensity. There are nine cicada sound recording files and twenty four cricket sound recording files. Cicada has high sound characteristic (9,168.2 Hz) and cricket has low sound characteristic (3,311.80 Hz). Comparation to Singing Insect of North America (SINA) database shows that the cicada’s sound is resemble to Tibicen marginalis and the cricket’s sound is resemble to Grylodes sigillatus.

Uncertain Effects of Linear Internal Waves on Convergence Zone Propagation in Deep Water

Zhang, L.; Chen, W., and Liu, D., 2020. Uncertain effects of linear internal waves on convergence zone propagation in deep water. In: Zheng, C.W.; Wang, Q.; Zhan, C., and Yang, S.B. (eds.), Air-Sea Interaction and Coastal Environments of the Maritime and Polar Silk Roads. Journal of Coastal Research, Special Issue No. 99, pp. 296–309. Coconut Creek (Florida), ISSN 0749-0208.The use of the convergence zone effect is an important means of underwater long-range target detection. Many uncertain factors (ocean fronts, ocean eddies, etc.) can lead to uncertainties of the sound field in the convergence zone. Linear internal waves are usually produced in the deep ocean, causing fluctuations of the sound velocity which are otherwise stable. Over long distances, linear internal waves will have a great influence on the propagation of sound waves. In this paper, a model of sound velocity fluctuation caused by linear internal waves is established, and the sound velocity field within a certain depth and distance range is obtained. The transmission loss is calculated using the ray mode parabolic equation underwater sound propagation model. The Monte Carlo method is then used to simulate the uncertainty of the sound field in the generated convergence zone. The results shows that the loss of sound propagation varies greatly when an internal wave propagates through the convergence zone. The uncertainty of the sound field in different convergence zones varies, and the uncertainty of the sound field increases with convergence zone range.

Classification of Urban Road Traffic Noise based on Sound Energy and Eventfulness Indicators

Noise energetic indicators, like Lden, show good correlations with long term annoyance, but should be supplemented by other parameters describing the sound fluctuations, which are very common in urban areas and negatively impact noise annoyance. Thus, in this paper, the hourly values of continuous equivalent level LAeqh and the intermittency ratio (IR) were both considered to describe the urban road traffic noise, monitored in 90 sites in the city of Milan and covering different types of road, from motorways to local roads. The noise data have been processed by clustering methods to detect similarities and to figure out a criterion to classify the urban sites taking into account both equivalent noise levels and road traffic noise events. Two clusters were obtained and, considering the cluster membership of each site, the decimal logarithm of the day-time (06:00–22:00) traffic flow was used to associate each new road with the clusters. In particular, roads with average day-time hourly traffic flow ≥1900 vehicles/hour were associated with the cluster with high traffic flow. The described methodology could be fruitfully applied on road traffic noise data in other cities.

Azimuthal and temporal sound fluctuations on the Chukchi continental shelf during the Canada Basin Acoustic Propagation Experiment 2017.

The Shallow Water Canada Basin Acoustic Propagation Experiment was conducted on the Chukchi Sea continental shelf from October 2016 to November 2017. The experimental goals were to access (1) long-range (basin-scale) and (2) short-range (shallow-water) spatial and temporal energy variation. This letter focuses on a 20-dB energy change of acoustic signals in the frequency band 700-1100 Hz from June to August 2017 occurring along two shallow-water tracks from a common source, correlated with the occurrence of an oceanographic event in the top 150-m water column due to a Pacific Water outflow from the Bering Sea and retreat of the Marginal Ice Zone.

Nonlinear auditory models yield new insights into representations of vowels.

Studies of vowel systems regularly appeal to the need to understand how the auditory system encodes and processes the information in the acoustic signal. The goal of this study is to present computational models to address this need, and to use the models to illustrate responses to vowels at two levels of the auditory pathway. Many of the models previously used to study auditory representations of speech are based on linear filter banks simulating the tuning of the inner ear. These models do not incorporate key nonlinear response properties of the inner ear that influence responses at conversational-speech sound levels. These nonlinear properties shape neural representations in ways that are important for understanding responses in the central nervous system. The model for auditory-nerve (AN) fibers used here incorporates realistic nonlinear properties associated with the basilar membrane, inner hair cells (IHCs), and the IHC-AN synapse. These nonlinearities set up profiles of f0-related fluctuations that vary in amplitude across the population of frequency-tuned AN fibers. Amplitude fluctuations in AN responses are smallest near formant peaks and largest at frequencies between formants. These f0-related fluctuations strongly excite or suppress neurons in the auditory midbrain, the first level of the auditory pathway where tuning for low-frequency fluctuations in sounds occurs. Formant-related amplitude fluctuations provide representations of the vowel spectrum in discharge rates of midbrain neurons. These representations in the midbrain are robust across a wide range of sound levels, including the entire range of conversational-speech levels, and in the presence of realistic background noise levels.

Origins of scale invariance in vocalization sequences and speech.

To communicate effectively animals need to detect temporal vocalization cues that vary over several orders of magnitude in their amplitude and frequency content. This large range of temporal cues is evident in the power-law scale-invariant relationship between the power of temporal fluctuations in sounds and the sound modulation frequency (f). Though various forms of scale invariance have been described for natural sounds, the origins and implications of scale invariant phenomenon remain unknown. Using animal vocalization sequences, including continuous human speech, and a stochastic model of temporal amplitude fluctuations we demonstrate that temporal acoustic edges are the primary acoustic cue accounting for the scale invariant phenomenon. The modulation spectrum of vocalization sequences and the model both exhibit a dual regime lowpass structure with a flat region at low modulation frequencies and scale invariant 1/f2 trend for high modulation frequencies. Moreover, we find a time-frequency tradeoff between the average vocalization duration of each vocalization sequence and the cutoff frequency beyond which scale invariant behavior is observed. These results indicate that temporal edges are universal features responsible for scale invariance in vocalized sounds. This is significant since temporal acoustic edges are salient perceptually and the auditory system could exploit such statistical regularities to minimize redundancies and generate compact neural representations of vocalized sounds.

A Study of Combustion Instability Mode in a Dual Swirl Combustor

The combustion instability in a dual swirl combustor was investigated experimentally. The effects of thermal power and combustor length on combustion instability were evaluated. Pressure and heat release fluctuation were measured simultaneously. In a conventional combustor, the frequency was decreased with increasing combustor length and decreasing thermal power. However, it showed different results with a dual swirl combustor. In regime 1 where thermal power was relatively high, the results showed same tendency with a conventional combustor. In regime 2 where thermal power was relatively low, the frequency was almost constant with increasing combustor length. It was found that a beating phenomenon occurred with increased combustor length in regime 2 by measuring sound pressure fluctuation. By confirming that beating phenomenon occurs only in regime 2, it is considered that beating phenomenon is the dominant factor of combustion instability in regime 2. This beating phenomenon inside combustion chamber greatly affected to combustion instability. The reason of the beating phenomenon seemed to be the difference oscillating period between main flame and pilot flame.

Efficient subtle motion detection from high-speed video for sound recovery and vibration analysis using singular value decomposition-based approach

High-speed cameras provide full field measurement of structure motions and have been applied in nondestructive testing and noncontact structure monitoring. Recently, a phase-based method has been proposed to extract sound-induced vibrations from phase variations in videos, and this method provides insights into the study of remote sound surveillance and material analysis. An efficient singular value decomposition (SVD)-based approach is introduced to detect sound-induced subtle motions from pixel intensities in silent high-speed videos. A high-speed camera is initially applied to capture a video of the vibrating objects stimulated by sound fluctuations. Then, subimages collected from a small region on the captured video are reshaped into vectors and reconstructed to form a matrix. Orthonormal image bases (OIBs) are obtained from the SVD of the matrix; available vibration signal can then be obtained by projecting subsequent subimages onto specific OIBs. A simulation test is initiated to validate the effectiveness and efficiency of the proposed method. Two experiments are conducted to demonstrate the potential applications in sound recovery and material analysis. Results show that the proposed method efficiently detects subtle motions from the video.

An Integrated Assessment of Changes in Brain Structure and Function of the Insula Resulting from an Intensive Mindfulness-Based Intervention

Mindfulness training is thought to alter both brain function and structure, yet these effects are almost always investigated and reported independently. In the present study, we combine these two approaches to provide a more complete description of the effects of a 6-week mindfulness-based health and wellness intervention. Region-of-interest analysis of brain structure revealed a significant increase in cortical thickness within the left-hemisphere posterior insula, a region that plays a role in auditory perception and interoception. We then examined changes in the resting-state functional connectivity (rs-FC) of this insula cluster and found two regions with which it displayed increased functional connectivity: one in the right-hemisphere ventrolateral prefrontal cortex (vlPFC) and another spanning parts of the left-hemisphere middle and superior temporal gyri (MTG/STG). Individuals with the greatest improvements in dispositional mindfulness showed the greatest increases in insular thickness as well as greater increases in rs-FC of the posterior insula with vlPFC and MTG/STG. The insula, vlPFC, and MTG/STG comprise a structurally connected network involved in, respectively, early auditory perception, the allocation of attention to changes in sounds, and the detailed analysis of fluctuations in sounds. Accordingly, these findings suggest a mechanistic account of the alterations in brain structure and function that underlie changes in auditory processing following a mindfulness-based intervention.

Effect of nonlinear internal wave on monostatic reverberation in the shallow water region with underwater sound channel

The effect of nonlinear internal wave on reverberation is investigated for the shallow water region having an underwater sound channel, which was observed during SAVEX15 experiment. When source is located near the channel axis, the reverberation from rough bottom is insignificant because of trapped modes not interacting with the bottom. However, when a nonlinear internal wave is present, the reverberation level increases since trapped modes transfer to bottom interacting modes due to sound fluctuation by the nonlinear internal wave. This trend can be explained by the coupled mode equation [(2014). J. Acoust. Soc. Am. 135, 610-625]. To theoretically describe the increase of bottom reverberation, we simplify the situation where two modes are present; one is a trapped mode and the other is bottom interacting mode. In the situation, the trapped mode transfers to the bottom interacting mode after its encounter with the nonlinear internal wave. The bottom reverberation has different patterns and levels before and after the internal wave, and thus, it highly depends on the distance between source/receiver and internal wave.

Signal Processing: Passive Acoustic in Fisheries and Marine Mammals

Signal processing with passive acoustic in fisheries and marine science learn the sound frequency range of fish, the intensity of the sound amplitude, sound fluctuations, and shape the sound patterns of the fish. Application of passive acoustic filed for marine fisheries and science detects the sound frequency range of fish, the intensity of the sound amplitude, sound fluctuations, and shape the sound patterns of the fish. Passive acoustic methods used to monitor marine mammals expressed. In general, the signal obtained from the ranimal record sounds is poor and difficult to determine from which directions it is produced, therefore it requires that require amplification/ strengthening. Bioacoustic research is needed to identify the communication language (acoustic communication) in mammals. Bioacoustic detect mammal-produced frequency ranges of sound, amplitude intensity of sound, voice fluctuation, and form sound patterns of mammals. Studying bioacoustic is inseparable from the science of underwater acoustics, biology of mammals, and the study of mammalian behavior. Generally bioacoustic include physiology of mammals organ that produce sound, earnings voice mechanism, sound characteristics of mammals, mammals sound-approaching mechanism, the hearing capacity of fish, and the evolution of the auditory system, and to obtain the frequency range of each sound produced by the dolphins (mammals). Environmental conditions and parameters (salinity and temperature) will greatly affect the value of the intensity and frequency generated from the target, the more extreme the environmental conditions, the lower value of the intensity and frequency generated

Understanding Noise in Twentieth-Century Physics and Engineering

��� Noise is a common experience in the contemporary world. Din from traffic, construction sites, factories, and neighbors bother urban residents. Radio listeners, television watchers, and mobile phone users have to endure statics and fading from time to time. Music lovers have debated whether jazz, atonal composition, rock and roll, rap, and abstract expressionism are art or nuisance. Scientists try to retrieve genuine signals from fluctuating data. Engineers design devices, software, or systems to filter out disturbance to the normal functioning of technology. Mathematicians and physicists examine randomness. Traders and economists attempt to predict markets’ future trends beneath highly irregular commodity prices. Decision makers cope with all kinds of uncertainty. No matter whether we understand the term as annoying sound or random fluctuations, we simply cannot live a life without encountering noise. Despite its ubiquity in modern times, noise has rarely been a focus of historical studies of recent science and technology. There may be an obvious reason for this lack of attention: noise largely reveals what science and technology are not, instead of what they are. Noise is an environmental plight of industrialization, an obstacle to the advancement of scientific knowledge, a subversive force to technology, a barrier to prediction, estimation, and control, and a symptom of disorder. As a result, noise often exposes the limitations of science and technology. While such limitations have played an important part in the development of science or technology, they are generally conceived as a background to this development, and thus scarcely become the subject of close investigations. A number of recent historiographical turns, however, have begun to change this situation. Inspired by the cultural histories of senses that flourished