مجله انجمن مهندسی صوتیات ایران
سال هشتم شماره 2 (پاییز و زمستان 1399)

Aquatic ecosystems are heterogeneous in terms of light and sound distribution. The aim of this study was to investigate the effect of environmental abiotic factors, light and sound stimuli, on Daphnia (Daphnia magna) swimming behaviour.  Here, we examined behavioural changes of Daphnia (N=24) in response to light and sound treatments simultaneously. The treatments concerned a 2×2 design with bright or dim light conditions and sound or quiet in an aquarium with dimensions 30×15×25 cm. Swimming behaviour changes were assessed include: the number of hops, swimming speed and spatial distribution time. The results showed that the number of hops increased significantly in the bright compared to the dim light treatment (P<0/05), while in the sound treatment, the number of hops did not significantly change compared to ambient treatment (P>0/05). The sound and bright light treatments increased swimming speed but these changes were not statistically significant (P>0/05). Also Daphnia spent more time in the lower layer of water in the dim light compared to the bright light treatment (P<0/05), while no significant difference was found between sound treatments on spatial distribution of Daphnia (P>0/05). More studies are needed to assess the multimodal effects of abiotic stimuli on the behaviour of aquatic species.

In this paper, the phonon, dynamic and thermal properties of indium nitride in two phases are investigated. The calculations are performed using the pseudopotantial method in the framework of density functional theory and by using the quantum-espresso Package. In the calculations, the exchange-correlation terms of LDA, GGA and PBE0 approximation are used. Investigation of phononic  properties shows that in this combination in the two phases Wz and Zb there is a frequency gap. From the study of thermal properties we find that the heat capacity drop is at low temperatures is as follos T3. At high temperatures, the heat capacity is also close to the Dulan-Petty law.The results from the phonon spectrum indicate that from the frequency of 209. 885 to 453 .112 cm -1 there is no acoustic and optical phonon modes and the most stable phase; Phase is the Wz.

The Acoustic Tomography (AT) systems are used to monitor long-term and continuous flow in rivers, seas and oceans. One of the disadvantages of existing systems in Iran is the inability of real-time/automated measurements. In this study, by adding a raspberry Pi computer to the system and performing the required programming, it was possible to do online monitoring. The data are transferred to the Raspberry Pi using the LAN and then sent over the Internet. Then, the 10-AT system was tested in Iranian waters. Two AT systems were installed on two fixed boats at a depth of 13 meters at a distance of 3 km from each other in the Caspian Sea. Their transducers were suspended at a depth of 6 meters. Acoustic signals were transmitted every minute. The results showed that the speed of sound and water velocity are 1460 and 0.2 m, respectively. Also, assuming the salinity to be constant, the water temperature was calculated 14 ˚C. Due to the facility of online monitoring of marine currents and the provision of environmental information, the use of this method in the coastal areas of the Caspian Sea, the Persian Gulf and the Makran coasts is recommended.

In this study, a method for non-invasive estimation of stress on the heart wall in  the diastole phase is presented using ultrasound echocardiography and tissue Doppler  imaging. The aim of this study was to evaluate the stress on the heart wall as a  pre-diagnosis  to identify people with coronary artery stenosis. 29 patients with stenosis of more than 70%, 30 patients with stenosis of 50 to 70% and 35 healthy human participated in this study as a control group. the average stress of anterior and intraventicular septum was estimated non-invasively by considering wall thickness, left ventricular dimensions, and end-diastolic pressure by Using 2D echocardiography, tissue Doppler and Doppler ultrasound imaging techniques. The statistical analysis results were shown significant difference between the estimated stress at the end of the diastole phase, between groups of patients with severe, moderate stenosis and healthy individuals in all wall segments. Patients with severe obstruction in the anterior descending coronary artery have more diastolic stress than patients with moderate stenosis and healthy humans. The average increase of end-diastolic stress in the longitudinal and radial directions based on percentage by incidence of moderate stenosis in the anterior wall is 12.6 and 13.4, and with severe stenosis is 57 and 103, respectively. In the septal wall, the average increase of end-diastolic stress in the longitudinal and radial directions based on percentage, is 9.1 and 17.6 in moderate stenosis, and with severe stenosis is 64 and 63.3, respectively. Therefore, it has been shown that wall stress at the end of the diastolic phase can be considered as an important non-invasive indicator in assessing myocardial function by examining and processing ultrasound echocardiography images for patients with coronary artery stenosis.

In this paper, a phoxonic crystal structure is designed that shows a complete phononic and photonic ban gap and is capable to guide the optical waves with transverse magnetic polarization and acoustic waves. The materials used in the structure are nylon and molybdenum, which have suitable refractive index and elastic constant. Also, it is worth of noting that the filling factor is 28% for the proposed structure, which causes easy fabrication. The proposed structure is a phoxonic filter that represents only a given frequency or wavelength in the output. This is performed by passing through ring resonators, having the minimal frequency width or wavelength. Given that it is difficult to match light and sound in phoxonic structures, the structure has advantages including better sound and light coupling between input and output, frequency and wavelength sharpness, and low frequency width or wavelength, compared to phononic or photonic ring resonator-based filters, due to the triangular ring and also causes the improvement of output results and increased output quality. Methods of finite element, plane wave expansion, and finite difference time domain are used for simulation.

The purpose of this numerical analysis is to deduce the temperature difference between the two heated wires of the sensor due to an imposed particle velocity. In this research, the effects of sensor geometric parameters such as changing the dimensions of the wires, the distance between the wires and How wires are placed over the sound direction. The sensitivity of sensors is investigated numerically. Numerical studies show that sensitivity is a function of frequency. With frequency increase from 100 to 1000 Hz, it is sharply reduced and then monotonic to zero. Also, been observed that the sensitivity is related to the position of the wires relative to each other and the dimensions of the cross-section of the wires, and sensitivity decreases by increasing the distance between the wires and the height of the cross section of the wires. Further, the sensitivity angle dependence has been investigated, and the observed sensitivity is related to how the wires are placed over the sound wave propagation and in parallel mode by increasing angle from zero to 90 degree, the sensitivity decreases.

One approach to speech recognition is to model speech based on a number of phonetic units. Because the frequency and temporal characteristics of vowels are more stable than other phonems, it is important to recognize vowels to distinguish speech. In this research, the aim is to present a model using modern methods, such as deep neural network to improve the accuracy of vowel recognition and increase its applications. 30 speakers (15 females and 15 males) read all the combinations of consonants with 6 Persian vowels. After preprocessing, the speech data is segmented into frames containing only the vowels and its spectrogram is extracted. These spectrogram are given as input to the neural network with two hidden layers. Speech of 25 speakers were used for training and speech of 5 speakers were used for testing. The average of accuracy of 6 Persian vowels for the proposed model was 93.17% (total average of vowel detection error is 6.83%). In previous works the average of vowel detection error was 9.7% to 19.6% that in proposed model improved from 2.87% to 12.77%.

Real time source localization is a difficult method and includes challenges such as computational complexity, noise, reflection and sensor layout architecture. The time difference of the arrival signal method is used because of its simplicity and low computational complexity and if the energy ratio of the signal is combined with the time difference of arrival the results will be somewhat improved. In this paper, a method for estimating the location of the speech source in a three-dimensional space is proposed to calculate the delay in the time difference of the arrival signals and noise resistance and reflection to sharpen the peak of the signal correlation. This method, while using the appropriate arrangement of sensors and applying phase spectrum smoothness while amplifying power along with cubic spline interpolation, to have high speed solution of nonlinear equation devices, improved Chan and weighted least squares two-stage algorithms with the ratio of sensor energy to signal, thus the basis sensor has benefitted. The mean error of the direct distance of the estimated coordinates from the true position of all measurements in the selected arrangement of the array in the Chan and weighted least squares two-stage combined with energy is 10.94 and 10.185 cm, respectively. The test results on real and simulation data show that the interpolation of cross-correlation and the combination of the energy ratio with the time difference of the arrival signal of the proposed method is efficacious.

Identify each sound source, is necessary in an acoustical field with multiple sources. In sound source identification, different techniques are used and the most important of all is based on artificial intelligent. The objective in this paper is to separate the gunshot sounds from other acoustical field sound sources. To implement the objective, a set of domestic data sets recorded inside Iran in different environmental conditions closed to real word operational situations are used to separate the gunshot sound sources from impulse environmental noise through a feature extraction technique based on wavelet transform combined with linear prediction coefficients and statistical momentum features of sound signals. Finally, different classification techniques are used on the extracted features to differentiate these gunshot sounds from other pulsed environmental noise. Also, different groups are specified to identify the sound of the sniper shot from other sounds generated by G3 and Kalashnikov rifles. The technique used in this paper has a 98.57 percent differentiation precision for separating gunshots from other pulsed sound sources via a cumulative classifier and 86.94 percent differentiation precision to separate the sound of sniper from the shot sounds of the G3 and Kalashnikov rifles.

The variety of effects induced in electrochemical processes by ultrasound can lead to the production, growth and collapse of micro-bubbles in the electrolyte.  The aim of this study was to investigate the effect of ultrasound and energy resulting from the collapse of microbubbles on the structure and catalytic efficiency of electrolytic manganese dioxide (EMD) for oxygen reduction reaction. In this study, MnO2 nanoparticles were first produced by sono-electrochemical and electrochemical methods with voltage of 2800 mV and then phase identification of nanoparticles by XRD method, particle size and shape by electron microscope, the molecular structure by Raman and the pore size bt BET methode were done. We tested these two samples on a Zinc-Air battery as electrocatalysis for Oxygen Reduction Reaction. To investigate the electrochemical properties, the battery polarization and battery discharge at different battery currents and battery charge and discharge were used. The charge discharge, polarization curve and power density of the battery showed that manganese dioxide synthesized by sono-electrochemical method had better performance than the other sample, as well as battery voltage dependence on discharge time compared for as the synthesized samples. Also the resuls showed that at different discharge current densities (5-10-20-50-100-150-200 mA) in sono-electrochemical nanoparticles correlation between potential/time is more than in electrochemical nanoparticles.

In this paper the elastic, mechanical (stability, anisotropy and Poisson's coefficients) and acoustic properties of BeX (X= S, Se, Te) have been investigated. Calculations with Full potential linear augmented plane wave have been performed in the framework of density functional theory with LDA, PBE-GGA and MBJ approximations by using Wien2k computational package. Elastic properties such as, elastic constants, Shear modulus, Young modulus and Debye temperature were calculated within various approximations for cubic and hexagonal structural phases. The calculated elastic properties indicate the give rise to an elastic stability and anisotropy property of the compounds. The results also indicate that these compounds are more brittle in the cubic phase and more malleable in the hexagonal phase. In fact, the ductility of these compounds in the cubic structural phase is low and they can be placed in the category of non-formable materials.

In the present study, by sending acoustic waves to an underground tunnel, as a free air explosion, and measuring the pressure level of the reflected waves to the surface and the transmitting waves to the interior space of the structure, the effects of the parameters, such as tunnel existence, soil nonlinear behavior, energy dissipated boundary conditions, soil density and modulus of elasticity are analyzed. Based on the results, it is observed that in the presence of the tunnel and by assigning the wave dissipated boundary conditions to the far ends of the model, the pressure level of the acoustic wave is reduced. Furthermore, it is resulted that the effect of the soil nonlinearity is negligible. It is illustrated that for the softer soils, although the energy dissipation is increased, because of the growth in vibrations due to the lack of soil solidity, the transmitted waves are amplified. Moreover, it is shown that the pressure level for the stiffer soils is more sensitive to the soil density variation than the softer ones. By comparing the present results with results extracted from the similar papers, it is concluded that the way the explosion modeled, the geometric properties of the tunnel section and the most important of all, the buried depth of the tunnel have significant effects on the behavior and trend of the reflected and transmitted acoustic waves for different models of soil around the tunnel.