Об'єктом дослідження є звукове поле від лінійних джерел звуку довкола шумозахисних екранів. Зменшення рівнів звуку за екраном в першу чергу обумовлено геометричними розмірами екрану та взаємним розташуванням екрана та джерела звуку. Впливу даних факторів приділялася велика кількість наукових публікацій. Однак проблемним місцем таких досліджень є те, що екрани вважались або повністю акустично жорсткими або звукопоглинальними. В даній роботі розглянуто ситуацію імпедансного екрану, що досить часто застосовується на практиці. Розрахунок поля довкола такого екрану проводився засобами комп'ютерного моделювання, що дозволяє легко змінювати величину акустичного імпедансу поверхні екрану. Для обчислення звукового поля довкола екрану було обрано метод скінченних елементів. Звукопоглинальні властивості екрана визначалися зміною акустичного імпедансу лицьової сторони екрана. При цьому екран залишався акустично непрозорим. Таким чином, було проведено аналіз впливу коефіцієнта звукопоглинання на звукове поле довкола екрана за різних висот екрану та відстані джерел звуку до екрана. Це дозволило отримати результати рівнів звукового тиску довкола екранів, що зустрічаються в інженерній діяльності. Проведені дослідження показали, що використання звукопоглинального облицювання шумозахисних екранів дозволяє збільшити їх ефективність. Виявлено, що чим ближче екран розташовано до джерела звуку, тим більший вплив його звукопоглинальних властивостей. Показано, що для низьких частот збільшення ефективності екрану за рахунок звукопоглинання може сягати величини 5 дБ. Отримані у ході дослідження результати можна використовувати при проектуванні шумозахисних екранів для зниження рівнів шуму від транспортних потоків. Особливо корисними отримані результати будуть при проектуванні екранів з висотами більше 4 м. Ключові слова: шумозахисний екран, дифракція звуку, зменшення рівня звуку, імпедансні властивості, звукопоглинальний екран.
This paper reports studying the reduction of traffic noise by rounded noise protection screens with finite sound insulation, that is, those that can pass sound. Almost all models of acoustic screens, which are examined by analytical methods, are either direct or such that disregard the passage of sound through the screen, that is, it is assumed that the screen sound insulation is non-finite. This approach made it possible to solve the problem for a simplified model analytically but made it impossible to analyze the required sound insulation of noise protection screens. In the current paper, the problem of investigating an acoustic field around the screen whose sound insulation is finite has been stated, that is, it was taken into consideration that a sound wave propagates through the body of the screen. In addition, a given problem considers a rounded screen, rather than vertical, which is also used in different countries. Such a problem was solved by the method of partial domains. This method has made it possible to strictly analytically build a solution to the problem by simplifying it to solving an infinite system of algebraic equations, which was solved by the method of reduction. The screen model was set by the values of the density and speed of sound in the screen material. This approach has made it possible to change the acoustic impedance of the screen material and thereby change the sound insulation of the screen. That has made it possible to quantify the effect of screen sound insulation on its effectiveness. It has been shown that the efficiency of noise protection screens with finite sound insulation is approaching the efficiency of acoustically rigid screens, provided that the screen's natural sound insulation is 13–15 dB greater than the estimated efficiency of the rigid screen. The study results could make it possible to more accurately assess the effectiveness of noise protection screens. Determining the screen acoustic efficiency would make it possible to set requirements for its sound insulation characteristics. That could make it possible to select the designs of noise protection screens with minimal physical parameters, such as thickness, weight, etc.
This paper reports a study into the acoustic field of transport flow around noise protection screens located on both sides of the sound source. Most research on noise protection involving noise protection screens relates to the assessment of the effectiveness of screens located on one side of the noise source. The influence of the second screen on the effectiveness of the first one has been investigated only experimentally. Therefore, it is a relevant task to assess the mutual impact of the two screens between which the linear sound source is located. A problem was stated in such a way that has made it possible to derive an analytical solution and find a sound field around a linear sound source. In this case, the sound source was limited on both sides by acoustically rigid screens with finite thickness. The screens' cross-sections were shaped as part of a ring with arbitrary angles and the same radius. The problem was solved by the method of partial domains. This method has made it possible to obtain an infinite system of algebraic equations that were solved by the method of reduction. Such an approach to solving a problem allows a given solution to be applied for different cases of the mutual location of screens, source, and territory protected from noise. The study results help estimate a field between the screens, the dependence of increasing sound pressure on the road on the geometric size of the screen and the width of the road. In addition, the solution resulted in the ability to assess the impact of one screen on the efficiency of another in the frequency range of up to 1,000 Hz. It has been shown that the mutual impact of screens could reduce the screen efficiency by 2 times. The study reported here could make it possible to more accurately calculate the levels of the sound field from traffic flows when using noise protection screens, which is often performed in practice when designing new and reconstructing existing highways.
The acoustic field of the traffic flow around the noise barriers located on both sides of the sound source has been investigated. The overwhelming number of publications devoted to the topic of noise protection with noise barriers concerns the assessment of the effectiveness of screens located on one side of the noise source. Investigation of the influence of the second screen on the efficiency of the first one, if it was investigated, then only by experimental research. In this work, a theoretical study of the mutual influence of two impedance screens, between which a linear sound source is located, is carried out. The problem is formulated in such a way that it made it possible to apply the method of partial regions for the analytical solution of the problem of finding the sound field around a linear sound source. In this case, the sound source is limited on both sides by impedance screens of appropriate thickness. By their shape, the screens are part of a circle with arbitrary corners and the same radius. When solving the problem, an infinite algebraic system of equations is obtained, which is solved by the reduction method. The results of such studies allow assessing the field both between screens and behind screens. This will make it possible to determine the effect of impedance surfaces simulating partial sound transparency on the acoustic field around such screens. This will allow assessing the effect of soundproofing screens on their effectiveness. Such studies will make it possible to more accurately calculate the sound field levels of traffic flows when using impedance noise barriers. It will also make it possible to reasonably put forward requirements for the minimum oundproofing capacity of the screen structure.
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