In this study, the seasonal variations of the sound speed in the water column and consequently the temperature and salinity in Babolsar area were investigated based on the field measurements. Data used in this study were carried out in two hot (summer) and cold (winter) seasons of 2019, from inshore to far offshore. The mixed layer depth was calculated using the seasonal combination threshold value of 1.25 (C°) for summer data and 0.1 (C°) for winter data. The results show that in the summer, due to the hot weather and increased stratification, the mixed layer depth is shallower than what is observed in winter. In winter, vertical convection increased due to the decrease in air temperature which leads to the deep mixed layer depth and in most of the stations whole water column is completely mixed. Consequently, whole column water surrounded with the sonic layer channel during the winter while in summer any sonic channel was observed. The surface temperature in summer is significantly higher than winter. Also, the thermocline slope is very strong in summer and very weak in winter.

Effect of saline and fresh water interference on sound speed variation in the basin of Anzali port has been evaluated. The research is based on the analysis of measured data of various physical parameters of sea water in the vicinity of Anzali port. Also, the effects of saline water of the Caspian Sea and fresh water imported from wetland on the changes in the sound speed in the access channel of Anzali port have been discussed. The data collecting operation was performed by a CTD profiler of the physical parameters of the seawater in fixed stations with a maximum depth of 18 meters in both warm and cold seasons. Results showed that sound speed changed between 1514 and 1511 m/s in the summer. While range of variation in the cold season, was between 1438 (at the surface) and 1454 m/s at 10 m depth. Variation of the sound speed during warm season was affected by water temperature. During cold season, variations of sound speed were under effect of water salinity and, sea saline and wetland fresh water interference. In comparison the results with previous measurements, it is observed that saline and freshwater interference on physical structure of water column and sound speed is considerable in cold season.

High quality of commercial and research uses of acoustical methods in fisheries need to have enough information about sound speed variations, Ray tracing and attenuation rate in (he water. in this paper we focused on sound speed variation with depth versus physical properties of Bandar Dayer waters (NE of Farsi island and about 50 kilo meters south of Delware; 28.2 N & 50.58 E) and calculation of attenuation rate. Importance of this area is for the Gulf currents, which cover this region. The results of this research show that up to 11 meters depth sound speed remain constant while depth increases and temperature decreases. After this depth sound speed decreases which is for decreasing in salinity-and temperature. Sound attenuation profiles show that the most attenuation rate is at 17 to 27 meters depth.

Real time positioning of sound sources suffers from computational complexity and low response time, which depends on the presence of noise, reflection and sensor layout architecture to increase the accuracy and speed of direction finding. Providing a scalable approach with low complexity, resistant to reflection and natural and artificial noise to increase the speed of decision making with appropriate architectural design is a new research topic in civilian and military applications. This paper proposes a fast scalable method of natural noise-resistant and reflective acoustic direction finding for three-dimensional estimation of direction finding using the signal time difference of arrival technique, which has a suitable sensor architecture and uses Phase Transform pre-filter along with cubic spline interpolation without pre-processing for noise removal uses a fast algorithm Successive Unconstrained Minimization. In real and artificial near field data experiments, the amount of Azimuth angle and Elevation error is 0. 5587 and 1. 1652 degrees, respectively, and in the far field is 0. 0321 and 0. 2759 degrees, respectively, and the real-time direction determination speed is 1. 006 Seconds. The high accuracy is the estimated angle and the main position of the source.

Thermodynamic properties of CO2 are derived from speed of sound in the temperature range 300 to 360 K (from 0 to 6 MPa), and 300 to 220 K (from 0 to 90% of the saturation pressure). The density, the specific heat capacity at constant pressure, and the specific heat capacity at constant volume are obtained by numerical integration of differential equations connecting the speed of sound with other thermodynamic properties. The set of differential equations is solved as the initial value problem, with the initial values specified along the isotherm at 300 K in terms of several accurate values of the density and the specific heat capacity at constant pressure. The density, the specific heat capacity at constant pressure and the specific heat capacity at constant volume are derived with the absolute average deviations of 0.018%, 0.19%, and 0.18%, respectively. The results of numerical integration are extrapolated to the saturation line for r, cp, and cv with the absolute average deviations of 0.056%, 2.31%, and 1.32%, respectively.

In consideration of physical and chemical properties of pure substances, speed of sound is one of important quantity which can used to calculate many of other thermo-physical properties such as isothermal compressibility, Joule-Thomson coefficient, isobaric heat capacity and etc. These thermo-physical properties are the main parameters in industrial and chemical processes. Development of accurate models for thermodynamic properties computation such as speed of sound is well expected above all in those fields where very high performance calculations have to be reached. In this present work, a new generalized model as a function of reduced temperature and reduced density is proposed to correlate speed of sound of methane, ethane, propane and butane halogenated refrigerants. Speed of sounds have been calculated and compared with data reported in literatures for 5600 data points of 28 refrigerants, and the overall average absolute percentage deviation of 0.92%. The source of speed of sound data used in this study is the NIST Chemistry Web Book.

High quality of commercial and research uses of acoustical methods in fisheries needs to have enough information about sound speed variations, Ray tracing and attenuation rate in the water. In this paper we focused on the sound speed variations versus depth for physical properties of Bandar Dayer (NE of Farsi island and about 50 kilometers south of Delwar, 282 N and 5058 E) and calculation of attenuation rate. Importance of this area is for the Gulf Currents, Which cover this region. The results of this research show that up to 11 meters of depth sound speed remains constant while depth increases and temperature decreases. After this depth, sound speed decreases which is a result of decreasing in slinity. Sound attenuation profiles show that the most attenuation rate is at 17-27 meters depth.

The internal waves complicate the propagation process of sound in the water.These waves are considered the main cause of disturbances in sound speed, and now it is known that the internal waves are the dominant parameter in the change process of sea frequency spectrum, as these changes range from many hourly cycles (floating frequency) to almost one daily cycle (inertia frequency).The profile of mass sound speed in shallow waters depends on salinity and temperature gradients in turbulence internal waves. Here, the assumption is that the only probability function source is the turbulence internal waves in a water column. This investigation aims to use the mathematical models to study the internal wave effects on propagation of sound waves in shallow waters and that the waves how affect the sound propagation and depend on what parameters? We used the data gathered from Persian Gulf to calculate the parameters such as: sound speed, floating frequency, the ratio of resulted turbulences in sound propagation by vertical movement, phase functions and internal wave domain. Meantime, based on a given wave length (in the study area: 235 m.), the shape of first mode has been compared to the other modes.The probability density functions have been calculated for two different modes.Comparing the ratio of generated turbulences in sound propagation by vertical movement and horizontal speed of particle, showed the horizontal movement is considerably less than the vertical one and also by increasing the depth (consequently decreasing the floating frequency), vertical movement is raised highly. The highest floating frequency and turbulences generated in sound propagation by vertical movement are found on the places near the water level and this is due to thermocline existence and on the other hand in the same places we have the lowest range of vertical movement.

The aerodynamic noise from the new high-speed Maglev train (NHMT) is significant. One way to reduce it is to use a fully enclosed sound barrier (FESB). This paper studies the aerodynamic noise characteristics of the NHMT operating inside a FESB at 600 km/h, taking into account the compressibility of air and the quadrupole sound sources. The transient flow field around the NHMT is simulated by adopting an improved delayed detached-eddy simulation. According to Lighthill acoustic analogy theory, the aerodynamic noise inside and outside the FESB can be simulated using the acoustic finite element method. The sound insertion loss (IL) of the FESB is analyzed by comparing the noise outside the FESB with the noise generated by the NHMT operating on open tracks. The results indicate that the noise is distributed in the streamlined shoulder area of the head and tail car and the wake. The far-field noise belongs to broadband noise, and the noise outside the FESB is similar to an incoherent line source. The IL of the FESB is 25. 2 dB(A) at 25 m from the track centerline and 3. 5 m above the track surface. Therefore, the noise reduction effect of a FESB is much better than a traditional upright sound barrier.

Today, there are many methods and equipment for estimating the speed of a moving vehicle, which many of them are expensive due to the installation conditions and requirements. One of these methods is the use of sound intensity quantity. Sound vector sensors, which are passive sensors, can obtain sound intensity values from the environment. In this article, using two sound vector sensors, the average speed of moving vehicles in circular paths is obtained. In this method, to get the speed, it is necessary to estimate the location of the source first. A sound vector sensor alone cannot determine the location of the sound source and can only estimate the direction of arrival (DoA). By using two sensors and determining the intersection of the rays of each sensor, the location of the sound source can be detected. The methods and equations governing this method are presented in this article. In the end, the numerical results are analyzed. In this article, various circular paths have been studied. The results show that the proposed method is good at estimating the location and speed of the moving vehicle at different times.