Road totally-enclosed sound barrier sound field prediction method and system

Abstract

The invention relates to the technical field of environmental acoustics, discloses a road totally-enclosed sound barrier sound field prediction method and system, belongs to the field of environmental acoustics, and has very high practicability in sound field prediction and noise pollution evaluation of public road traffic noise after a totally-enclosed sound barrier is implemented. On the basis of the acoustic propagation principle, a new prediction method is provided for a road traffic noise source and a totally-closed sound barrier, a sound field is divided into two subsystems including a barrier internal space and an external space, and equivalent acoustic models of the two subsystems and a calculation method and recommendation parameters of the noise source sound power level are given respectively. According to the method, the sound environment of the high-rise building close to the urban road can be accurately predicted and calculated, and a basis is provided for noise pollution evaluation and control. And meanwhile, the method can be matched with a national standard method or commercial acoustic software for use, and has relatively high applicability.

Description

Technical Field

[0001] This invention relates to the field of environmental acoustics technology, and in particular to a method and system for predicting the sound field of a fully enclosed road sound barrier. Background Technology

[0002] In some cities, roads or elevated highways are located very close to sensitive residential buildings. To meet environmental protection requirements, fully enclosed sound barriers are often implemented. According to fire safety regulations, smoke exhaust openings are typically installed at the top of the barrier, using segmented designs in strip, circular, or square shapes. After the implementation of fully enclosed barriers, some traffic noise energy inside the barrier is radiated outwards after being sound-insulated by the barrier structure, while some propagates through the smoke exhaust openings at the top of the barrier, causing noise pollution to the surrounding environment, especially high-rise buildings.

[0003] The "Technical Guidelines for Environmental Impact Assessment - Acoustic Environment" (HJ 2.4-2021) specifies engineering methods for calculating outdoor sound propagation attenuation based on GB / T 17247.1 and GB / T 17247.2, used to predict noise generated by various types of sound sources at a distance. However, the method for calculating noise attenuation caused by sound barrier shielding is only applicable to simple, vertical sound barriers and cannot be used to calculate noise attenuation from barriers with complex top structures or fully enclosed sound barriers.

[0004] Currently, commercial acoustic prediction software, such as the German Cadna / A software, lacks a prediction model for fully enclosed sound barriers, only allowing equivalent calculations using a "vertical-inward-folded" barrier model. This type of environmental acoustic prediction method is based on the outdoor sound propagation model in ISO 9613, employing Fresnel theory to calculate the insertion loss of the sound barrier. However, after the implementation of a fully enclosed barrier, only a small smoke vent exists at the top, creating a closed space inside the barrier, which differs significantly from the semi-free sound field of a vertical side screen. Using this type of acoustic software for calculations presents the following problems: firstly, it does not consider the reverberation effect of the barrier's internal space; secondly, the inward-folded barrier and sound ray model cause sound field distortion in some calculation areas. Taking Cadna / A software as an example, using a vertical inward-folded barrier and setting a large inward fold depth to equivalently calculate the erroneous sound field distribution is as follows: Figure 1 As shown.

[0005] The finite element-boundary element method based on wave theory can establish sound barrier models with complex structures and acoustic properties with high computational accuracy, but the modeling is complex. When calculating environmental noise, which is mainly of medium and high frequency, a huge computational grid is required, resulting in high time costs. It is difficult to apply in large-scale environmental noise prediction and noise reduction engineering design.

[0006] In summary, there is currently no accurate and easily applicable prediction method for the sound field of fully enclosed road sound barriers. Summary of the Invention

[0007] The main objective of this invention is to solve the technical problem of difficulty in applying existing sound barrier models to the sound field prediction of fully enclosed road sound barriers. A method for predicting the sound field of a fully enclosed road sound barrier includes the following steps: The internal space of the fully enclosed sound barrier is considered as a diffuse sound field, and the sound pressure level at a designated receiving point within the internal space is calculated. The fully enclosed sound barrier is modeled as an equivalent surface sound source, and the sound power level of each surface sound source is calculated. Define a directivity correction factor for each of the aforementioned surface sound sources; Based on the sound power level and directivity correction factor of each surface sound source, the total sound pressure level at the predicted point in the external space of the fully enclosed sound barrier is calculated.

[0008] A second aspect of the present invention provides a sound field prediction system for a fully enclosed road sound barrier, comprising: The sound pressure level calculation unit is used to treat the internal space of the fully enclosed sound barrier as a diffuse sound field and calculate the sound pressure level at a specified receiving point within the internal space. The sound power level calculation unit is used to model the fully enclosed sound barrier as an equivalent surface sound source and calculate the sound power level of each surface sound source. A directivity correction factor definition unit is used to define a directivity correction factor for each of the area sound sources; The total sound pressure level prediction unit is used to calculate the total sound pressure level at prediction points in the external space of a fully enclosed sound barrier based on the sound power level and directivity correction factor of each surface sound source.

[0009] The present invention has the following beneficial effects: The sound field prediction method for fully enclosed road sound barriers described in this invention solves the problems of the lack of domestic standard calculation methods and the deficiencies of commercial acoustic software in scenarios requiring sound field prediction for fully enclosed sound barriers.

[0010] The prediction method of this invention has high accuracy, a simple modeling and calculation process, and fast computation speed, making it applicable to large-scale environmental noise prediction calculations. It has significant practical value for urban road noise pollution assessment and control engineering. Attached Figure Description

[0011] Figure 1 This is a diagram illustrating erroneous calculation results from commercial software.

[0012] Figure 2 This is a schematic diagram of a fully enclosed sound barrier structure. Figure 3 This is a schematic diagram of sound ray propagation in a rectangular space. Figure 4 A two-dimensional cross-sectional space for a fully enclosed sound barrier Schematic diagram; Figure 5 This is a schematic diagram of a surface sound source model; Figure 6 Directional correction factor Value selection diagram; Figure 7 This is a flowchart of a method for predicting the sound field of a fully enclosed road sound barrier.

[0013] Figure 8 This is a schematic diagram of a fully enclosed sound barrier project as an example.

[0014] Figure 9 For example, the directional correction factor Calculated value.

[0015] Figure 10 The sound field prediction results (sound pressure level contour map) are shown in the example. Detailed Implementation

[0016] The terms “first,” “second,” “third,” “fourth,” etc. (if present) in the specification, claims, and accompanying drawings of this invention are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments described herein can be implemented in orders other than those illustrated or described herein. Furthermore, the terms “comprising” or “having,” and any variations thereof, are intended to cover a non-exclusive inclusion; for example, a process, method, system, product, or apparatus that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus.

[0017] For ease of understanding, the specific process of the embodiments of the present invention is described below. Please refer to [link / reference]. Figure 1 The first embodiment of the sound field prediction method for fully enclosed road sound barriers in this invention includes: The internal space of the fully enclosed sound barrier is considered as a diffuse sound field, and the sound pressure level at a designated receiving point within the internal space is calculated. The fully enclosed sound barrier is modeled as an equivalent surface sound source, and the sound power level of each surface sound source is calculated. Define a directivity correction factor for each of the aforementioned surface sound sources; Based on the sound power level and directivity correction factor of each surface sound source, the total sound pressure level at the predicted point in the external space of the fully enclosed sound barrier is calculated.

[0018] The total sound pressure level at the prediction point in the external space is calculated using the following formula. : in, The sound power level for each surface sound source; Directivity correction factor defined for each surface sound source; Outdoor sound propagation attenuation is calculated using national standard models or commercial acoustic software.

[0019] The principle of this invention is as follows: Based on the idea of ​​statistical energy analysis, the internal and external spaces of the fully enclosed barrier are divided into two subsystems. and .

[0020] The fully enclosed sound barrier and its internal space are considered as a whole as a subsystem The components that radiate acoustic energy outward in this subsystem are the screens on the left and right sides. Top screen and the top smoke exhaust opening For external space, these components can be considered equivalent to surface sound sources with specific sound power levels and directivity. The sound field can be calculated from the propagation attenuation law of surface sound sources outdoors.

[0021] First, the internal space subsystem is given. Sound field calculation method. The exhaust vent at the top of a fully enclosed sound barrier is relatively small compared to the entire barrier. Within a long section of the barrier, it can be approximated as a closed space, and the continuous flow of traffic in the lane can be approximated as a line sound source. The sound source emits countless sound rays in all directions, which reflect multiple times between the road surface and the screen, such as... Figure 2 As shown. From a statistical point of view, it can be assumed that the sound rays are independent of each other, have the same probability of propagation in all directions, and have a uniformly distributed average sound energy density inside the space, that is, the space inside the barrier is a diffuse sound field.

[0022] In subsystem A two-dimensional plane space is formed by taking a cross section inside. A 2.5D noise prediction model was established. When the road and barriers extend for a long time, the sound power and sound field distribution of the sound sources in any space along the route are approximately the same. (Two-dimensional planar space) The mean free path of sound rays emitted by an internal sound source is independent of the cross-sectional shape, and can be simplified to a rectangular space for analysis and calculation. (Linear sound source) Generalized to an omnidirectional two-dimensional point sound source ,like Figure 3 As shown.

[0023] First, calculate the rectangular space. Mean free path of internal sound ray propagation. Defined space. Internal point source For road traffic vehicle noise sources, the sound source Sound rays are emitted only in the upper semi-circular plane, with the number of sound rays emitted per second being [number missing]. Calculated by equation (1).

[0024] In the formula, The number of sound rays per unit plane angle.

[0025] Sound source per 1 second All the sound emanating in space The total number of collisions and reflections occurring on the four walls is calculated using equation (2).

[0026] In the formula, , Rectangular spaces Length and width; The angle of sound radiation; Let the speed of sound in air be denoted as ; and define . rectangular space circumference, ; rectangular space area, ; rectangular space Internal sound source Emit all sound chords across the total distance within 1 second Calculated by equation (3).

[0027] rectangular space The mean free path of the sound ray from the internal sound source is calculated by equation (4).

[0028] From rectangular space Expanded into a two-dimensional cross-sectional space of a fully enclosed sound barrier ,like Figure 4 As shown.

[0029] When the sound source Sound power per unit length At that time, point sound source in two-dimensional space average radiated power Acceptance Point The sound energy at a given location includes the direct sound energy radiated from the sound source and the reverberant sound energy within the space. When the reverberation within the space reaches dynamic equilibrium, the steady-state reverberant average sound energy density is defined as... It can be calculated from equations (4) and (5).

[0030] In the formula, the definition is... The barrier section constant is defined as follows: Two-dimensional cross-sectional space inside the barrier The outer perimeter of the contour; Perimeter The average sound absorption coefficient of the medium is negligible because the equivalent frequency of road traffic noise is usually below 1kHz. Substitute equivalent average absorption coefficient; space Total average energy density of internal sound field For the superposition of direct sound and reverberant sound energy, the direct sound energy density It can be calculated using equation (6).

[0031] In the formula, For the point of acceptance To the sound source The straight-line distance; The total average energy density is obtained by combining equations (5) and (6). The equilibrium equations are as shown in equations (7) to (8).

[0032] In the formula, For receiving point Effective sound pressure at the location; The density of the sound propagation medium; when propagating in the air, Desirable .

[0033] Sound pressure level at receiving point P It can be transmitted through a line sound source. The sound power level per unit length is expressed as in equation (9).

[0034] Road traffic noise sources are located close to the road surface, resulting in significant reflections from the road surface and the sides of barriers. When the sound absorption coefficients of the road surface and barriers are low, the impact of reflections on direct sound energy cannot be ignored. Therefore, the subsystem... Internal receiving point sound pressure level at Finally, it is calculated by equation (10).

[0035] In the formula, As a directional factor, its value mainly depends on the side screen. The sound absorption coefficient is such that when it is greater than 0.5, only road surface reflection needs to be considered, and the reflection from the screen itself can be ignored. When the sound absorption coefficient is less than 0.5, .

[0036] Sound power level per unit length of the equivalent line sound source for road traffic noise It is calculated using the following formula: in It is the equivalent continuous A-weighted sound pressure level at a horizontal distance of 7.5m and a height of 1.5m outside the centerline of the road when the traffic flow is stable; It is the equivalent continuous A-weighted sound pressure level at a horizontal distance of 25m and a height of 2.5m outside the centerline of the road when the traffic flow is stable.

[0037] Furthermore, the external space subsystem is given. The modeling and calculation method. In the external space of the sound barrier, the radiating sound source is equivalent to the screen on the left and right sides. Top screen and the top smoke exhaust opening A surface sound source with the same spatial location and geometric dimensions is used, and this surface sound source is discretized into an infinite number of point sound sources. Subsystem The acoustic energy received at a point on the boundary of any cross-section of a surface is attenuated through the boundary (sound insulation of the barrier) and then radiated outward. When extended to three-dimensional space, the acoustic energy at that point, minus the transmission loss, is equivalent to the source intensity of the sound at that discrete point in a surface sound source. For a subsystem with a defined cross-section... and The sound power of the surface sound source is uniformly distributed, and the sound power per unit area is... It is calculated from equation (11).

[0038] In the formula, The sound pressure level at the inner boundary of the barrier is obtained by equation (10); The value is the boundary transmission loss; for the side screens and top screens, it can be approximated as the sound insulation of the screen; for the smoke exhaust opening, the value is taken as 0 without considering the scattering at the opening edge.

[0039] The above subsystems Defined , as well as Surface sound source model, such as Figure 5 As shown. A surface sound source propagation directivity correction factor is defined in its normal direction. , The range of values ​​is defined in the polar coordinate system, with the direction of the surface sound source normal as the 0-degree axis and the deflection angle as the axis. They exhibit a mapping relationship and are symmetrically distributed about the normal axis, such as Figure 6 As shown.

[0040] for and , The value of is determined by equation (12); for , The value of is determined by equations (13) and (14).

[0041] In the formula, The sound source is located inside the barrier, with the opening at the top of the barrier serving as the sound source. The central axis is the vertical reference plane, representing the total number of lanes on one side; This represents the average width of the lane. Sound source for the opening at the top of the barrier Height above the road surface.

[0042] After completing the modeling of the above subsystems, the calculation method for the prediction points of the external space sound field is as follows. Calculate the area sound source separately. , as well as The outdoor sound propagation attenuation to the prediction point is calculated, and the sound level at the prediction point is calculated as shown in Equation (15).

[0043] In the formula, For each surface sound source distance Predicted sound pressure level at the location; The sound power level for each surface sound source; The directional factor determined by equations (12) to (14); Outdoor sound propagation attenuation can be calculated using national standard models or commercial acoustic software, which will not be elaborated upon in this invention.

[0044] Predicted total sound pressure level It is calculated from equation (16).

[0045] In the formula, This represents the total number of equivalent surface sound sources in the model.

[0046] The aforementioned prediction model requires the sound power level of the equivalent line source of road traffic noise as input. There are three main methods: 1. Calculation using existing empirical formulas based on parameters such as traffic flow and speed; 2. Calculation using commercial acoustic software; 3. Obtaining the power level through on-site analog measurements. Methods 1 and 2 already have mature technical solutions, and this invention will not repeat them. Only the testing and calculation methods for method 3 are proposed.

[0047] Noise benchmark measuring points 1 and 2 were set up on one side of an unobstructed, straight road. Under stable traffic conditions, the equivalent continuous A-weighted sound pressure level at each measuring point was monitored over a period of time and denoted as [the noise level is recorded as 1]. . This represents the horizontal distance of the measuring point from the center line of the road.

[0048] Measuring point 1 was set at a horizontal distance of 7.5m and a height of 1.5m from the centerline of the road. The equivalent continuous A-weighted sound level was recorded as follows: .

[0049] Measuring point 2 was set at a horizontal distance of 25m from the centerline of the road and a height of 2.5m. The equivalent continuous A-weighted sound level was recorded as follows: .

[0050] Sound power level per unit length of the equivalent line sound source for road traffic noise Calculated using equation (17).

[0051] In summary, the method for predicting the sound field of a fully enclosed road sound barrier described in this invention has the following process: Figure 7 As shown.

[0052] The sound field prediction method for fully enclosed road sound barriers in the embodiments of the present invention has been described above. The sound field prediction device for fully enclosed road sound barriers in the embodiments of the present invention is described below: The sound pressure level calculation unit is used to treat the internal space of the fully enclosed sound barrier as a diffuse sound field and calculate the sound pressure level at a specified receiving point within the internal space. The sound power level calculation unit is used to model the fully enclosed sound barrier as an equivalent surface sound source and calculate the sound power level of each surface sound source. A directivity correction factor definition unit is used to define a directivity correction factor for each of the area sound sources; The total sound pressure level prediction unit is used to calculate the total sound pressure level at prediction points in the external space of a fully enclosed sound barrier based on the sound power level and directivity correction factor of each surface sound source.

[0053] To better understand the present invention, the invention will be further explained below with reference to the accompanying drawings and specific embodiments.

[0054] This example illustrates a sound field prediction case for a fully enclosed sound barrier project on an elevated road in a certain location. The project's plan is shown below. Figure 8 As shown.

[0055] In this embodiment, a fully enclosed sound barrier is installed on the northern section of the elevated road. The barrier's side panels are sound-absorbing panels, the top is an acrylic light-transmitting panel, and a 2-meter-wide smoke exhaust opening is left in the middle. There are several residential buildings on both sides of the road barrier, and environmental noise measuring points N1 and N2 are arranged at different distances from the buildings. At the same time, a noise benchmark measuring point N3 is arranged on the road section without the barrier.

[0056] Based on the actual site conditions, the engineering parameters of the sound barrier were obtained, and the barrier constant was calculated as shown in Table 1.

[0057] Table 1 Using the test values ​​at test point N3, the equivalent line source sound power level of road traffic noise is calculated according to equation (17), as shown in Table 2.

[0058] Table 2 The directivity correction factor for each surface sound source was calculated based on the engineering geometric parameters. The result is as follows Figure 9 As shown.

[0059] The predicted vertical sound field distribution is as follows: Figure 10 As shown in Table 3, the predicted and measured results for each measuring point are presented in the table below. The results in Table 3 demonstrate that the sound field calculated by this prediction method does not exhibit distortion and conforms to the actual situation of noise propagation. The predicted results for sound field points N1 and N2 deviate from the monitoring results by less than 0.5 dB(A), indicating good accuracy.

[0060] Table 3 The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for predicting the sound field of a fully enclosed road sound barrier, characterized in that, Includes the following steps: The internal space of the fully enclosed sound barrier is regarded as a diffuse sound field, and the sound pressure level at a specified receiving point in the two-dimensional cross-section of the internal space is calculated. The fully enclosed sound barrier is modeled as an equivalent surface sound source, and the sound power level of each surface sound source is calculated. Define a directivity correction factor for each of the aforementioned surface sound sources; Based on the sound power level and directivity correction factor of each surface sound source, the total sound pressure level at the predicted point in the external space of the fully enclosed sound barrier is calculated.

2. The method according to claim 1, characterized in that, The two-dimensional cross-section of the internal space Designated Acceptance Point sound pressure level at The calculation formula is: in, As a directional factor, when the sound absorption coefficient is greater than 0.5, When the sound absorption coefficient is less than 0.5, R is the barrier cross-sectional constant, and r is the straight-line distance from the receiving point to the sound source. This represents the sound power level per unit length of the equivalent line source for road traffic noise.

3. The method according to claim 2, characterized in that, The sound power level per unit length of the road traffic noise equivalent line sound source It is calculated using the following formula: in It is the equivalent continuous A-weighted sound pressure level at a horizontal distance of 7.5m and a height of 1.5m outside the centerline of the road when the traffic flow is stable; It is the equivalent continuous A-weighted sound pressure level at a horizontal distance of 25m and a height of 2.5m outside the centerline of the road when the traffic flow is stable.

4. The method according to claim 2, characterized in that, The barrier section constant R is calculated using the following formula: in, The perimeter of the outer contour of the two-dimensional cross-sectional space inside the barrier; Perimeter The average sound absorption coefficient.

5. The method according to claim 1, characterized in that, The total sound pressure level at the prediction point in the external space is calculated using the following formula. : in, The sound power level for each surface sound source; Directivity correction factor defined for each surface sound source; Outdoor sound propagation attenuation is calculated using national standard models or commercial acoustic software.

6. The method according to claim 5, characterized in that, For the surface sound sources on the left and right side screens and the top screen, the directivity correction factor The value of is determined by the following formula: Where θ is the deflection angle between the propagation direction and the normal direction of the surface sound source.

7. The method according to claim 5, characterized in that, For the sound source at the opening of a fully enclosed sound barrier, the directivity correction factor The value of is determined by the following formula: in, The total number of lanes on one side of the barrier, with the central axis of the sound source at the top of the barrier as the vertical reference plane; This represents the average width of the lane. θ is the height of the sound source at the top opening of the barrier from the road surface; θ is the deflection angle between the propagation direction and the direction of the surface sound source normal.

8. A sound field prediction system for a fully enclosed road sound barrier, characterized in that, The system includes: The sound pressure level calculation unit is used to treat the internal space of the fully enclosed sound barrier as a diffuse sound field and calculate the sound pressure level at a specified receiving point within the internal space. The sound power level calculation unit is used to model the fully enclosed sound barrier as an equivalent surface sound source and calculate the sound power level of each surface sound source. A directivity correction factor definition unit is used to define a directivity correction factor for each of the area sound sources; The total sound pressure level prediction unit is used to calculate the total sound pressure level at prediction points in the external space of a fully enclosed sound barrier based on the sound power level and directivity correction factor of each surface sound source.

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