DETERMINATION OF THE INHOMOGENEITY PARAMETERS OF A SPHERE’S COVER ENSURING REQUIRED SOUND REFLECTION IN A WAVEGUIDE

The numerical-analytical method of identifying the inhomogeneity parameters of a material of a sphere’s elastic cover, which allow to ensure minimal (maximal) average pressure in the scattered field of a spherical sound wave, which is radiated by a monopole source, within the disk observation domain in a cylindrical waveguide, has been developed. The sphere is assumed to be either absolutely rigid (moveless) or filled with an homogeneous elastic material. Verification of the scheme for determining the cover’s extremal inhomogeneity characteristics has been carried out and influence of the solution algorithm’s launch parameters on their identification accuracy during the numerical experiment has been evaluated. The finite element method (FEM) and the Hooke-Jeeves algorithm are used in the problem solving.

CRITICAL REVIEW OF METHODS FOR EVALUATING ACOUSTIC CHARACTERISTICS OR PREMISES

Introduction: The development of effective structural materials with improved acoustic characteristics is relevant for the modern construction industry. Considering the variety of international building standards for acoustic insulation and soundproofing of buildings, it is essential to systematize the modern methods of studying these characteristics. The purpose of the study was a comprehensive review of methods for determining acoustic characteristics in construction, as well as an analysis of literature and international standards to improve the health and comfort of the urban population.Main part: Due to the variety and complication of the study of the acoustic characteristics of buildings, premises and individual walling, the article provides an analysis of methods for evaluating these characteristics. The limitations on the size of rooms and sound frequencies for measuring reverberation time have been identified. The process of improving the method of measuring acoustic impedance in Kundt’s tube is shown. The methodology for determining the numerical parameters of sound insulation in buildings using the study of building envelopes taking into account the spectra of various noise sources located inside and outside the building is considered in detail. It was found that existing methods for measuring impact noise show poor reproducibility in the low frequency range. The analysis of the works proved that the sound reflection characteristics theoretically depend on the thickness and rigidity of the reflecting surface and its surface density.Conclusions: The scope of building materials with improved acoustic characteristics is quite extensive. Further research may be aimed at improving methods for studying the characteristics of sound absorption and sound reflection.Financial transparency: the authors have no financial interest in the presented materials or methods. There is no conflict of interest.

Pengukuran Kecepatan Suara dalam Media Air Menggunakan Sensor Ultrasonik

The speed of sound in water varies depending on the condition. There are several factors that affect the difference in the speed of sound in water, such as the viscosity, temperature, pressure, etc. In this study, designed a tool to measure the speed of sound in water by utilizing ultrasonic waves.The ultrasonic sensor used consists of transmitter and receiver. The method used is indirect method by using sound reflection. The 40kHz ultrasonic wave used on the transmitter is generated by the AD9850 signal generator. Signals received receiver in and processed on a microcontroller through an LM393 comparator that makes the signal HIGH and LOW so it can be read directly on the digital pins of microcontroller.Measurements were made at a water temperature of 27oC with 1 meter test medium. The measurement is done on variation of distance from 5-90 cm with span of 5 cm. By knowing the time difference between the transmitted and received signal and the known wave range, the speed of sound in the water obtained in the study was (1394 ± 27) m / s with the determination coefficient of 0.998.

Complete Lung Ultrasound Using Liquid Filling: A Review of Methods Regarding Sonographic Findings and Clinical Relevance

(200w) Lung ultrasound (LUS) is widely used for the diagnosis of pulmonary diseases such as solid nodules and consolidations in contact with the pleural cavity. However, sonography for processes of central disease remains impaired due to total sound reflection at the air tissue interfaces in the ventilated lung. These acoustic barriers can be overcome by replacing intra-alveolar air with liquid. Such filling has been reported using perfluorocarbon, saline or emulsions out of those. In order to achieve acoustic access enabling the use of LUS, complete gas free content is required. Such lung tissue - liquid compound will have untypical physical properties that might impact upon the sonographic visualization of central structures. Up to now, the filling of the lung has been reported for very specific applications and not classified regarding their sonographic findings. This work was therefore motivated to review the literature for methods of lung liquid instillation, classifying their methodological strength and limitations for achieving acoustic access and sonographic findings. Finally, their use for ultrasound based clinical applications will be discussed and the need for research will be outlined.