A review of research progress in air-to-water sound transmission

International and domestic research progress in theory and experiment and applications of the air-to-water sound transmission are presented in this paper. Four classical numerical methods of calculating the underwater sound field gener- ated by an airborne source, i.e., the ray theory, the wave solution, the normal-mode theory and the wavenumber integration approach, are introduced. Effects of two special conditions, i.e., the moving airborne source or medium and the rough air-water interface, on the air-to-water sound transmission are reviewed. In experimental studies, the depth and range distributions of the underwater sound field created by different kinds of airborne sources in near-field and far-field, the longitudinal horizontal correlation of underwater sound field and application methods for inverse problems are reviewed.

The Effects of Seamounts on Sound Propagation in Deep Water

A propagation experiment was conducted in the South China Sea in 2014 with a flat bottom and seamounts respectively by using explosive sources. The effects of seamounts on sound propagation are analyzed by using the broadband signals. It is observed that the transmission loss （TL） decreases up to 7 dB for the signals in the first shadow zone due to the seamount reflection. Moreover, the TL might increase more than 30 dB in the converge zone due to the shadowing by seamounts. Abnormal TLs and pulse arrival structures at different ranges are explained by using the ray and wave theory. The experimental TLs and arrival pulses are compared with the numerical results and found to be in good agreement.

Study on Reduction of Mixed Water Salinity by Sound Wave <br/>—Toward Water Scarcity Issue-Solving in Isolated Islands in the World

There are so many Isolated Islands (inhabited islands) in the world, including Japan. However, at present islanders, there have been faced with the decline of industries, serious concerns of rapid aging and very low birthrate without children and water scarcity issues etc. It can be said that these situations are under the environment which shows a microcosm of Japanese and/or world survival society in the near future. In this paper, the experimental data on the reduction of the mixed water (seawater & rainwater) salinity by the sound wave when changing the volume ratio were first shown, taking into the characteristics of the Isolated Islands. Next, the main analysis result on the water qualities of mixed water with which sound wave was irradiated was shown and the consideration mainly based on the WHO drinking water quality standards was carried out. Finally, through a simple water quality improvement apparatus using small hydroelectric power, a consideration regarding a possibility of the purification of the water (to be a drinking water) based on the solar circulation energy (regenerative type’s natural energy) such as small hydropower utilization, natural sunlight utilization, natural gravity utilization, natural oscillation utilization has been described in the paper.

Use of Total Precipitable Water Classification of A Priori Error and Quality Control in Atmospheric Temperature and Water Vapor Sounding Retrieval

This study investigates the use of dynamic a priori error information according to atmospheric moistness and the use of quality controls in temperature and water vapor profile retrievals from hyperspectral infrared （IR） sounders. Temperature and water vapor profiles are retrieved from Atmospheric InfraRed Sounder （AIRS） radiance measurements by applying a physical iterative method using regression retrieval as the first guess. Based on the dependency of first-guess errors on the degree of atmospheric moistness, the a priori first-guess errors classified by total precipitable water （TPW） are applied in the AIRS physical retrieval procedure. Compared to the retrieval results from a fixed a priori error, boundary layer moisture retrievals appear to be improved via TPW classification of a priori first-guess errors. Six quality control （QC） tests, which check non-converged or bad retrievals, large residuals, high terrain and desert areas, and large temperature and moisture deviations from the first guess regression retrieval, are also applied in the AIRS physical retrievals. Significantly large errors are found for the retrievals rejected by these six QCs, and the retrieval errors are substantially reduced via QC over land, which suggest the usefulness and high impact of the QCs, especially over land. In conclusion, the use of dynamic a priori error information according to atmospheric moistness, and the use of appropriate QCs dealing with the geographical information and the deviation from the first-guess as well as the conventional inverse performance are suggested to improve temperature and moisture retrievals and their applications.

Effect of ocean environmental factors on sound absorption by boric acid relaxation in sea water

By using the expressions for the maximum absorption per wavelength (αλ),and the relaxation frequency fr of the boric acid relaxation derived previously by the author and employing the related oceanographic literatures, the effects of pressure, temperature, pH and salinity on (αλ)r and ∫r of the boric acid relaxation in sea water have been estimated. Results show that ( αλ), not only increases with pH but also increases approximately linearly with pressure and temperature, and is nearly proportional to the 1. 35 power of salinity. However, pressure, pH and salinity have negligible effect on ∫r; therefore, ∫r, can be approximately expressed as a function of temperature only. Comparisons of the predicted with the measured ( αλ)r and ∫r in different ocean areas are given.

Geoelectric Soundings for Delineation of Saline Water Intrusion into Aquifers in Part of Eastern Dahomey Basin, Nigeria

This study was aimed at mapping the subsurface extent of saline water intrusions into aquifers at the eastern part of Dahomey basin, Nigeria. The study adopted geoelectric sounding methods. 108 vertical electrical soundings (VES) and 9 induced polarization soundings (IPS) data were acquired using Schlumberger array technique. Three aquifer units were delineated across the study area. The resistivity of the first, second and third aquifer layers varies from 0.2 to 1569 ohm-m, 0.5 to 904 ohm-m and 0.4 to 665 ohm-m respectively, while depth to the top of first, second and third aquifer varies respectively from 0.7 to 151.5 m, 1.4 to 305.5 m and 12.9 to 452.9 m. The depth to the first aquifer layer is shallow (less than 5 m) in the coastal area which makes this area to be highly vulnerable to anthropogenic pollution while their proximity to Atlantic Ocean makes them susceptible to saline water intrusion. In all the three aquifer units, the coastal area, Agbabu and other few locations in the mainland are characterized by low resistivity values (below 60 ohm-m) indicating possible presence of brackish or saline water. IP sounding results showed that all the low resistive layers in the mainland are characterized by clayey materials. The integration of VES and IPS results enabled the delineation of the saline water lateral extent across the study area. There is a strong direct correlation (r2 = 0.8564) between location distance from the saline water source and depth to saline water in the study area. This can therefore serve as a predictive model to determine depth to saline water at any location within the saline water zone in the study area.

Design of P-FLANN Model for Intelligent Water Fountain Sound Pleasantness Monitoring Using Bio-inspired Computing and Human Speech Perception

Cognitive-inspired computational systems play a crucial role in designing intelligent health monitoring systems which help both patients and hospitals.It also helps in early and consistent decision-making for various health issues including human psychological health.Water fountains built in parks and public spaces are used as decorative instruments which not only give appealing visuals but also provide a relaxing environment to the visitors.These natural sounds have a direct effect on the psychological health of visitors.Very few research works are reported on developing the relationship between water sounds and their corresponding psychological impact.This assessment needs trained manpower and a lot of experimental time which is costly and may not be always available.In this paper,to access the from the pleasantness from human health-friendly water fountain sounds,a perceptually weighted functional link artificial neural network(P-FLANN)model is developed.To reduce the computational complexity of training and for faster convergence,swam intelligence-based optimization algorithm is used for updating the weights.It is observed from the comparative simulation results that the proposed P-FLANN model can effectively perform prediction tasks which is not only cost-effective but also 95%accurate and can play a crucial role in designing human health-friendly water fountains in smart cities.

Modeling the Underwater Acoustic Field Excited by an Airborne Rapidly Moving Source Using Wavenumber Integration

It is complicated to model the acoustic field in stratified ocean for airborne aircraft,due to high speed of the source and air-to-water sound transmission.To our knowledge,there are very few papers in the open literature dealing with this complicated problem;but,in our opinion,they all require great amount of computation.We now propose a different method that requires much less computation.We improve the wavenumber integration method to model the received temporal signal for a moving source in stratified ocean and sum up in a concise form the core of our paper as follows:(A) Eq.(11) can be calculated by means of fast Chirp Z transform and the signals at all N time points are generated simultaneously;(B) direct numerical evaluation of the wavenumber integral in Eq.(4) produces large numerical errors;so it is necessary to shift the integration slightly below the real axis;(C) we compare the computation cost of direct calculation method with that of our fast calculation method;from the results presented in table 1,we can see that the fast calculation method consumes much less computation time,particularly for long duration signals;(D) for an airborne rapidly moving source,we compute the Doppler-shifted signals in shallow water and analyze their short-time Fourier transform;from Fig.1b,we can see that the received signals have multiple frequency components for a tonal source due to source motion and that each component corresponds to an arrival path.

Study on Sustainable Water Resource Conservation—Toward Deepening of Homo Environmentics

To unlearn the meaning of a sustainable water resource conservation is now an essential issue in using of sustained, sound, and high-quality water in the world. In this paper, a water quality purification by the Schumann frequencies was first considered through the murmuring sound of upper reach at the mountain stream (Kyoto Pref., Japan) regarding the conservation of water resources. Second, water is changing freely and easily accepting the wavelength of all the sounds. We therefore referred to a flow and dynamic equilibrium to realize and understand the water quality purification process. Finally, a “consciousness only Buddhist philosophy” of water quality as an analogical approach was introduced to realize and understand the water purification process. As a result, we have confirmed the water purification capability by Schmann frequencies in an experiment on water quality. And through the experiment, we have realized the importance/significance to find the meaning for a person’s primary meaningless such as 1) meaning connection among life, environment, and economics as a condition of human life, 2) energy, entropy and fluctuation under law of thermodynamics, 3) a metaphor between water quality and mutual possession of the ten worlds based on conscious-only theory, and 4) sense of wonder through the water purification process.

Environmental Anthropological Study of Watershed Management‐Water Quality Conservation of Forest as a Catchment Area in the Southern Part of Australia

Authors have conducted an experiment of irradiation using sound waves (frequency) including ultrasonic waves into water such as drinking water, sea water and forest water and wastewater so far. As a result, almost the same effect of improvement of water quality was confirmed for each sound wave. Then, an environmental anthropological study of watershed management based on the sound was carried out assuming that a water quality management using the sound could be possible. The Goulburn River basin in the southern part of Australia in which indigenous peoples (Yorta Yorta) have been concerned with the management for a long time so far was selected as an objective drainage basin this time. As a result, a couple of environmental anthropological perspectives on watershed management were proposed.

Sea Water Intrusion Modeling in Rashid Area of Nile Delta (Egypt) via the Inversion of DC Resistivity Data

The current research focuses on the detection of sea water intrusion in Rashid area which is located about 75 km east to Alexandria, Egypt. For this purpose, geoelectrical survey was carried out using the Schlumberger Vertical Electric Sounding (VES) to identify freshwater thickness, sea water intrusion and estimate subsurface lithology. Seventeen VES stations were measured with current electrode separation (AB/2) ranging from 1.5 m to 100 m. Then, the VES data was interpreted using 1-D and 2-D inversion schemes of DC resistivity data based on least squares method with smoothness constrains. The inverted resistivity distribution at relatively shallow depth shows an important low resistivity zone that probably reflects salt water alteration zone (northern parts). Depth to the freshwater bearing layer reaches its maximum at the south and decreases towards the north. From quantitative interpretation, invasion of salt water started at depth about 10 m at north in the thickness of freshwater bearing layer ranging from 15 to 25 m, while at depth of about 120 m all the layers were saturated with salt water.

New Method in Calculating the Trajectory of Sound Waves at Stratified Ocean

There is a new method of calculating the trajectory of sound waves (rays) in layered stratified speed of sound in ocean without dispersion. A sound wave in the fluid is considered as a vector. The amplitudes occurring at the boundary layers of the reflected and refracted waves are calculated according to the law of addition of vectors and using the law of conservation of energy, as well as the laws that determine the angles of reflection and refraction. It is shown that in calculating the trajectories, the reflected wave must be taken into account. The reflecting wave’s value may be about 1 at certain angles of the initial wave output from the sours. Reflecting wave forms the so-called water rays, which do not touch the bottom and the surface of the ocean. The conditions of occurrence of the water rays are following. The sum of the angles of the incident and refracted waves (rays) should be a right angle, and the tangent of the angle of inclination of the incident wave is equal to the refractive index. Under these conditions, the refracted wave amplitude vanishes. All sound energy is converted into the reflected beam, and total internal reflection occurs. In this paper, the calculation of the amplitudes and beam trajectories is conducted for the canonical type of waveguide, in which the speed of sound is asymmetric parabola. The sound source is placed at the depth of the center of the parabola. Total internal reflection occurs in a narrow range of angles of exit beams from the source 43° - 45°. Within this range of angles, the water rays form and not touch the bottom and surface of ocean. Outside this range, the bulk of the beam spreads, touching the bottom and the surface of the ocean. When exit corners, equal and greater than 77°, at some distance the beam becomes horizontal and extends along the layer, without leaving it. Calculation of the wave amplitudes excludes absorption factor. Note that the formula for amplitudes of the sound waves applies to light waves.

综合物探方法在碎屑岩地区找水中的应用——以云南宣威大路边村为例

为探索地球物理方法在碎屑地区找水应用的有效性,文章以云南宣威大路边村为研究对象,选取高密度电阻率法、联合剖面法、音频大地电磁法对碎屑岩层进行找水研究。结果表明:三叠系上统飞仙关组(T1f)碎屑岩富水性中等,含水性较均匀;受地面场地狭窄限制,高密度电法及联合剖面法测线长度有限,探测深度较浅,受碎屑岩电阻率小的影响,其找水应用效果不佳,在可探测的深度范围内较难识别基岩裂隙等找水有效异常,需结合其他物探方法甄别异常;音频大地电磁法找水应用效果相对较好,具有较高的横向分辨率,可有效识别碎屑岩中的断裂破碎带及构造裂隙带,表现为相对低阻异常特征;视电阻率单支测深曲线能有效分辨不同深度的岩土层结构,具有较高的纵向分辨率,对裂隙破碎带有较好指示意义。在地面场地较为狭窄的碎屑岩地区开展找水工作,音频大地电磁法结合视电阻单支测深曲线能取得较好效果,以音频大地电磁法确定碎屑岩地区中的裂隙发育带位置,以视电阻单支测深曲线确定裂隙发育带的深度。

基于四水听器的充水弹性管声速测量方法

实验室中水声材料声学参数的测量主要在水声声管中进行。管内平面波声速是正确测量这些参数的基础。该文提出一种基于四水听器结合不同边界的测量充水弹性管中声速的新方法。该方法利用4个固定位置处的水听器,采用最小二乘的方法,使得两组水听器分别得到的声管末端入射波声压差值的平方最小的声速即为管内平面波声速。该方法利用单频信号,在每一频率点均可测得声速,可以在任一种声管末端边界下进行测量,同时无需知道各水听器到边界的精确距离,在文中的3种边界下声速测量结果具有很好的一致性,实验操作简单、误差很小。该方法的仿真结果与管内声速的理论值吻合得很好,同时实验测量结果与仿真值之间的误差很小,证明了方法的准确性以及鲁棒性,为声管声速测量提供一个很好的思路。

金属声屏障用陶粒吸声板制备及性能实验研究

陶粒吸声板耐候性好、对环境影响小,是一种极具潜力的吸声材料,应用于金属声屏障需要深入研究其吸声、隔声性能。基于多孔材料的声学机理,通过振动加压成型技术,制备了陶粒吸声板,研究不同因素对其吸声、隔声性能的影响。测试结果表明:不同工况陶粒吸声板吸声系数、隔声量曲线趋势基本一致,中低频区段吸声系数逐渐增加,1000 Hz左右达到峰值,1000~5000 Hz吸声系数曲线存在波动及第二峰值;隔声量曲线基本呈先降低后增加趋势,区间存在波动,5000 Hz达到峰值;陶粒吸声板采用的陶粒粒径越小,吸声系数、隔声量越高;骨胶比由3.5提升至5.0,吸声系数、隔声量降低;降低水胶比,高频区段吸声系数增加明显,中高频隔声量降低明显;板厚增加,中高频段吸声系数曲线有向低频平移趋势,隔声量整体变化不大;陶粒吸声板放入金属外壳形成单元板后,吸声系数、隔声量较单一陶粒板整体提升显著。经过设计配比陶粒吸声板可以达到Ⅱ级吸声要求,同时兼具一定的隔声效果,放置入金属外壳组成声屏障单元板后,满足TB/T 3122—2019《铁路声屏障声学构件》标准要求,将陶粒吸声板用于金属声屏障吸声材料是可行的。

水浸超声线聚焦探头发射声场测量方法

航空构件常用小直径棒材进行加工制造,棒材的缺陷检测成为保证构件加工和使用质量的重要手段。但水浸超声点聚焦检测柱形或球形工件时易发生声束发散,检测灵敏度低下,而水浸超声线聚焦探头作为小直径棒材曲面检测的特殊应用,其声场分布决定了探头的检测能力与检测效率,因此线聚焦探头声场测量对小直径棒材检测具有重要意义。选取三只标称频率均为10 MHz,水中焦距分别为25 mm、38 mm、60 mm以及一只探头标称频率为15 MHz,水中焦距为20 mm水浸线聚焦超声探头。分别采取大平底、Φ3.18 mm的球靶和Φ1.5 mm的钢棒作为反射体,通过三轴自动化装置带动探头运动,得到不同反射体所测量的探头声场特性参数,并对测量结果进行对比,分析线聚焦探头声场测量方法。结果表明采用钢丝调整后球靶法可得到线聚焦探头较为准确的声场分布,采用钢丝法结合球靶法能够能到线聚焦探头较为准确的声场特征参数。

冲激声源棒-环型电极特性仿真研究

基于液电效应的水下脉冲放电技术产生的冲激声源被广泛应用于震源模拟、油田解堵增产、管道除垢、结石破碎和污水处理等领域。其中冲激声源的产生受到回路参数、间隙距离等多种因素影响。研究分析各因素对冲激声源的影响规律,有助于促进冲激声源的进一步应用。该文对棒-环电极结构的水下等离子体放电过程进行数值模拟,采用有限元分析方法对棒-环电极结构进行理论研究,得到不同初始条件对冲激波特性的影响作用。该文基于棒-环型电极结构,研究充电电压和电极间隙对棒-环型电极结构的影响,目的是为找寻冲激波更强、频带更宽、能量更高的声源。该文对研究棒-环型电极的实际应用提供参考。

采煤工作面水流声的降噪算法研究

采煤工作面水害事故发生前伴有水流声出现,为减小常见机械设备噪声对水流声识别的影响,提出了一种改进小波阈值降噪法。为了补偿水流声在采集过程中高频信号的损失,对其进行了预加重、分帧、加窗等预处理;采用小波软、硬阈值函数折衷法对阈值函数进行改进,避免了信号处理后带来的附加振荡问题;在固定阈值中引入了分解层数j,变化的阈值可最大程度分离水流声信号与噪声信号。结果表明,改进小波阈值降噪法相较于谱减法、子空间法和小波阈值法的硬阈值函数,输出信噪比提高了1 dB以上,降噪性能提升了15%左右;相较于小波阈值法的软阈值函数,当输入信噪比大于0 dB时,输出信噪比提高1 dB以上,可有效降低水流声信号中的机械设备噪声干扰。

关中地区持续性强对流天气成因分析及对农业的影响

为探讨关中地区罕见持续性强对流天气的成因和发生机理,客观分析此次过程对农业的影响情况。利用中国新一代全球大气/陆面再分析产品,常规高空、地面观测以及人工观测冰雹等资料,对2021年7月一次罕见持续性强天气的天气形势、水汽通量散度、假相当位温和环境参量以及影响农业生产的气象干旱指数、风雹对经济林果撞击深度等进行定量化客观分析。结果表明:此次关中地区持续性强对流天气受大气长波调整影响,前期以高空冷平流强迫类配置为主,后期属低层暖平流强迫类;低层偏东气流输送、副高外围西南暖湿气流、明显的水汽辐合和假相当位温密集区扩大造成显著的位势不稳定,是强对流天气发生的有利水汽和热力条件。较大对流有效位能、不稳定层结、垂直风切变增加和适当特殊层高度是强对流天气发生的有利潜势。强对流天气发生为旱情缓解和有效改善土壤墒情做出了积极贡献,但局地强降水和大风冰雹天气导致关中部分农作物倒伏,农田出现积水或土壤过湿现象,不利于玉米、猕猴桃等浅根系作物根部呼吸和养分输送,影响植株正常生长。关中地区多种经济林果出现0.07~0.32 cm的撞击深度,并出现脱落受损现象。研究结果为进一步加强农业气象服务和防灾减灾提供可靠依据。

基于声音空间化技术的自来水厂二氧化氯安全消毒方法

为提升自来水厂二氧化氯消毒的安全性,提出一种基于声音空间化技术的自来水厂二氧化氯安全消毒新方法。该方法采用了声波相控阵技术、超声波空化效应增强技术及声学共振耦合消毒优化技术,在降低二氧化氯使用量的同时显著提高了消毒效率和安全性。实验结果证实了该方法的可行性,为解决传统二氧化氯消毒工艺的局限提供了新思路。