In this article, an attempt has been made to estimate the amount of Sound transmission loss in a flat oval channel by applying the approach of statistical Energy analysis. Correct estimation of Sound transmission loss in an air conditioning channel is of great importance due to the harmful effects of noise pollution in the environment on human health. Simulation with the statistical Energy analysis method is a powerful approach to estimate Sound and vibration in problems in which we deal with complex and multi-part systems; is considered. In this method, first, a system is divided into several subsystems, and then by writing a matrix equation that includes the Energy exchanges between subsystems and Energy loss coefficients; It is investigated from the perspective of vibration and Sound estimation.On average, the model presented in this research is able to estimate the Sound transmission loss in different dimensions of the air conditioning channels according to the experimental results in the accuracy range of ± 2.5 dB. Considering that it seems that the results obtained from modeling with this method are in good agreement with the experimental data; The results of this research can be used as an efficient approach to estimate noise in oval shaped channels stretched in different lengths.

Sound is one of the forms of mechanical Energy and the two main characteristics of Sound are intensity or power and frequency or wavelength of Sound.their performance against the incoming Sound wave, industrial silencers can be divided into two general groups of resonating and absorption silencers, the main difference between these silencers is the release of Sound Energy from the channeling system, which is one of the common examples of the use of resonating type silencers, their use in It is the internal combustion engines that distinguish absorption silencers from the resonator type based on the fact that the main and visible part of the act of muting the Sound is achieved by changing Sound Energy to heat Energy.The goal of this article is to design a muffler based on the breaking of Sound frequencies resulting from the movement of fluid in the exhaust output of vehicles, which leads to a reduction of at least 50 db of Sound and gives the operator enough peace and concentration. In this article, after examining three types of mufflers, absorbent mufflers that use the properties of porous absorbent material to absorb passing Sound and are the simplest form of mufflers, have been selected, analyzed and reviewed and are suitable for the OM457 engine of Idem Industrial Company. It designed for maximum inlet exhaust temperature is 520 and for the maximum kW power is 315 with the maximum discharge relative pressure of 185 mbar for homogenization with the standard atmosphere.

Our contribution consists of studying numerical methods based on finite element space and finite difference schema in time of the linear one-dimensional thermoelastic Bresse system with second Sound. We establish some a priori error estimates, and present some numerical analysis results of discrete Energy under different decay rate profiles. Moreover, we study the behaviors of discrete Energy with respect to the system parameters and the initial data. Some numerical simulations will be given in order to validate the theoretical results.

The ultrasonic velocity of lanthanide chlorides in aqueous t-butanol has been determined, using a single-crystal interferometer at 25, 30, 35 and 40°C. The velocities are accurate to ±0.003%. The velocity data are correlated with lattice energies of the substances on the basis of Kudriavtsev's theory. The agreement between the calculated and experimental values is good at low concentration (C£0.03 mole/liter) of electrolytes containing structure-breaking ions, while it becomes poor with a further increase in concentration. The discrepancy is believed to be due to the invalidity of the theory in the case of higher valance electrolytes, such as rare-earth chlorides. It has been observed that, almost at any concentration, the apparent lowering of velocity is in the order of gadolinium chloride> samarium chloride> neodymium chloride, while lanthanum chloride> neodymium chloride at low concentration and is reversed as the concentration increases. The results are discussed in the light of the structure-breaking property of the ions studied.

In this study, the acoustic properties of porous absorbents with different porosity levels have been evaluated using different mathematical models. These models use one or more parameters of materials for calculating acoustic characteristics. In all of these models, materials are considered as equivalent fluid and reactionary characteristics have not been taken into account.

In this paper, geometries of architecture have been identified which convert maximum Sound and oscillation energies to thermal Energy without any kind of absorbers to minimize mount of noise in spaces through the geometry of space with absorbing the maximum Sound energies. Research has been done with COMSOL5. 2 software and simulation method. The argument of this research has been done through the logical reasoning and with tes t developing in selective software and has been documented and resulted. In process of research, Sound with 8000 HZ frequency that simulated a human speech, has been played in spaces with diverse form (changes in form of walls, ceilings) and same materials and has been calculated the mount of intensity, pressure and Sound pressure level. Then mount of Sound absorbing and converting to thermal Energy has been simulated in spaces with applying the absorbing rate of air and results has been documented from temperature change dependence to geometry of spaces. It is so important that the walls, ceilings and floors were adiabatic and insulate completely from inside. In Simulation processes, air has been used as a material that is filled inside of simulated forms and there has been not any kind of other materials. By obtaining numerical results, the most suitable geometries are identified for producing heat through the Sound oscillations and minimizing the noise. As a result, it was found that geometry of building make potential for Acous tic and thermal comfort from Sound Energy without any kind of absorbing materials inside of rooms. Heating changes simulated in two kind of geometries: pure volume and composite volume. Composite volumes have been choosing through the result of pure volume. Between pure volumes, Cylinder produced maximum temperature through the Sound energies. Considering cylinder as a regular polygon with infinity corners and sides and making corners in composite volumes, heating changes oscillated due to corners between sides. Corners with angel about to 90 degree produce more heat compared with other corners. A plurality of corners with 90 degree and equal sides adjacent to angle in geometry of architectural spaces change the mount of temperature in increasing ways. Corners with obtuse angles cause higher temperature and corners with acute angles produce lower temperature. The highes t temperature happens in geometries with 90 degree angles. Number of corners with obtuse and acute angles did not follow the definitive rules to produce heating or cooling in this study. The Bes t position for making consecutive corners in plans with right corners is the upper third of the height of Architectural spaces that produce high temperature. In compact geometries, the heat generated due to Sound energies and oscillations are more than geometries with s tretching in one direction. A Cube produces more heat than rectangle with same amount of height and volume. Composite of Cylinder and cube volumes in walls by maintaining the corners with 90 degree angles, lead to increasing the temperature. Filleted angles in walls of cubes and rectangles, with radius of ¼ of side of cube and more, make temperature increasing.

In this paper, the acoustic behavior of automotive cavity components is Investigated. For this purpose, by the aid of numerical simulation, the effects of using porous layer insulation in different parts of the cavity are studied. The numerical simulation is based on Statistical Energy Analysis; therefore, at the first stage the governing equations for the Statistical Energy Analysis are presented. Then, all internal and external components of the car body are divided into small subsystems. Herewith, the internal and external cavities of the car body have been identified. In the following, considering that the method of Statistical Energy Analysis is based on Energy storage and transmission, connections between all components of the model are created. Then, with applying all the Sound sources into the model, the effects of using porous materials on Sound transmission loss in some of the main components of the car body, including the roof, floor and dashboard panels are investigated. The results show that using of Sound insulations in different parts of the car, especially on the roof, improves the noise reduction to the cavity.

Muffler is one of the main components of an automotive exhaust system, which reduces the noise of the exhaust system. In this paper, modeling and simulation of the acoustic behavior of a muffler is presented with the aid of an engineering software. For this purpose, firstly, an analytical model is presented to evaluate the Sound transmission loss in cylindrical shells based on Sander's theory. Then, catalytic converter and muffler are modeled by considering the model's major dimensions in the engineering software. The comparison of the present results with previous studies shows the accuracy of the analytical model as well as the simulation results. In addition, the contour of Sound pressure inside the catalytic converter and the muffler, as well as the direction of the exhaust gas flow inside the muffler, indicate that the Sound level created by Muffler is in the safe range according to the limitations posed by the standards.