Method for far field noise prediction of a multiple unit train

Abstract

The application discloses a kind of far-field noise prediction methods of multiple unit train, comprising: establishing multiple unit train model, multiple unit train model includes sequentially arranged head car, intermediate car and tail car, and intermediate car includes at least one compartment;Set head car, compartment and tail car as linear sound source of same sound power;Set sound receiving point, sound receiving point is located in one side of multiple unit train model, and with interval from multiple unit train model, the line of sound receiving point and the center point of multiple unit train model is perpendicular to the running direction of multiple unit train model, and the noise sound pressure intensity of sound receiving point is calculated.By calculating the noise sound pressure intensity of sound receiving point, finally obtain the relationship between the noise sound pressure intensity of sound receiving point and the number of multiple unit train model, realize the purpose of predicting the noise sound pressure intensity of sound receiving point by the number of multiple unit train model.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of aerodynamic noise analysis of high-speed trains, and more particularly, to a far-field noise prediction method for a multi-formation train. BACKGROUND

[0002] It is difficult to analyze the aerodynamic noise of a high-speed train. The high-speed train runs close to the ground at high speed, and includes many complex structures such as a pantograph, a bogie, and a windscreen. The grid quantity and the calculation quantity rapidly increase with the increase of the formation length of the train, which brings great challenges to the evaluation of the far-field noise. Due to the limitations of the current aerodynamic noise calculation method and the calculation resources, it is usually difficult to evaluate the far-field noise of a multi-formation train. It is impossible to directly calculate the aerodynamic acoustics to obtain the far-field noise of a high-speed train with sixteen formations.

[0003] Therefore, it is an urgent problem to provide a far-field noise prediction method for a multi-formation train. SUMMARY

[0004] Therefore, the present application provides a far-field noise prediction method for a multi-formation train, comprising:

[0005] establishing a multi-formation train model, the multi-formation train model comprising a head car, intermediate cars, and a tail car arranged in sequence, the intermediate cars comprising at least one car;

[0006] setting the head car, the car, and the tail car as linear sound sources with the same sound power;

[0007] setting a sound receiving point, the sound receiving point being located on one side of the multi-formation train model and having a spacing from the multi-formation train model, the line connecting the sound receiving point and the center point of the multi-formation train model being perpendicular to the running direction of the multi-formation train model, and calculating the noise sound pressure intensity of the sound receiving point according to the following method:

[0008]

[0009] wherein L p is the noise sound pressure intensity of the sound receiving point, p0 2 is the reference sound pressure square, p 2 is the sound pressure square generated by the multi-formation train model at the sound receiving point, A is a constant, and N is the formation number of the multi-formation train model.

[0010] Preferably, the sound pressure square p 2 generated by the multi-formation train model at the sound receiving point is calculated according to the following method:

[0011]

[0012] wherein p i 2 is the sound pressure square generated by the single said car at the sound receiving point, +N / 2 is the multi-formation train model located in the interval from the end of the head car away from the tail car to the center point of the multi-formation train model, and -N / 2 is the multi-formation train model located in the interval from the end of the tail car away from the head car to the center point of the multi-formation train model.

[0013] Preferably, along the direction of the tail car pointing to the head car, the single said car includes opposite first and second ends, and the sound pressure square p i 2 The calculation is performed according to the following method:

[0014]

[0015] wherein ρ is the air density, c is the air speed, ω1 is the sound power per unit length of the single said car, r is the vertical distance between the sound receiving point and the single said car, θ1 is the included angle between the direction of the sound receiving point pointing to the first end and the direction perpendicular to the running direction of the multi-formation train model, and θ2 is the included angle between the direction of the sound receiving point pointing to the second end and the direction perpendicular to the running direction of the multi-formation train model.

[0016] Preferably, the angle formed by the sound receiving point and the multi-formation train model is also calculated, along the direction of the tail car pointing to the head car, the single said car includes opposite first and second ends, and the calculation is performed according to the following method:

[0017] The vertical distance between the sound receiving point and the multi-formation train model is set to 25 meters, and the length of the single said car is 25 meters;

[0018]

[0019] wherein θ1 is the included angle between the direction of the sound receiving point pointing to the first end and the direction perpendicular to the running direction of the multi-formation train model, θ2 is the included angle between the direction of the sound receiving point pointing to the second end and the direction perpendicular to the running direction of the multi-formation train model, +N / 2 is the multi-formation train model located in the interval from the end of the head car away from the tail car to the center point of the multi-formation train model, and -N / 2 is the multi-formation train model located in the interval from the end of the tail car away from the head car to the center point of the multi-formation train model.

[0020] Preferably, it further includes:

[0021] A measuring point is arranged at the center position of the top of each said car, and the sound pressure spectrum curve corresponding to each said measuring point is obtained respectively;

[0022] determining whether the sound pressure spectrum curves corresponding to each of the measuring points coincide;

[0023] if the sound pressure spectrum curves coincide, the sound powers of all the carriages are the same.

[0024] Preferably, the sound pressure square p generated by a single carriage at the sound receiving point is calculated. i 2 Further comprising:

[0025] Supposing that the length of a single carriage is D, the sound power per unit length of the single carriage is ω1, and the sound power corresponding to a length of dx is ω1dx, dx is taken as an infinitely small value, and the point sound source is taken as a point sound source, the sound pressure square p generated by the point sound source at the sound receiving point is calculated according to the following method:

[0026]

[0027] wherein d(p1 2 ) is the differential value of the sound pressure square p generated by the point sound source at the sound receiving point, and d is a differential symbol.

[0028] Preferably, the mean square sound pressure of the point sound source is calculated according to the following method:

[0029]

[0030] wherein p1 2 is the mean square sound pressure of the point sound source, ω is the sound power of the point sound source, and r i is the distance between the point sound source and the sound receiving point.

[0031] Preferably, the noise sound pressure intensity of the sound receiving point increases with the increase of the number of the multiple unit trains, but the slope decreases with the increase of the number of the multiple unit trains.

[0032] Preferably, when the number of the multiple unit trains increases to a limit value, the noise sound pressure intensity of the sound receiving point is constant.

[0033] Preferably, the number of the multiple unit trains N≥3.

[0034] Compared with the prior art, the multiple unit train far-field noise prediction method provided by the present application at least has the following beneficial effects:

[0035] The application provides a far-field noise prediction method of a multi-formation train, wherein a head car, a car and a tail car are set as linear sound sources with the same sound power, a problem of slightly large noise source intensity caused by a pantograph existing above the car is ignored, and influence of special properties of the head car and the tail car is ignored.

[0036] Of course, implementation of any product of the present application does not necessarily need to achieve all the technical effects described above.

[0037] Other features and advantages of the present application will become apparent from the following detailed description of exemplary embodiments thereof, taken in conjunction with the accompanying drawings. BRIEF DESCRIPTION OF DRAWINGS

[0038] The accompanying drawings incorporated in and forming a part of the specification illustrate embodiments of the present application and, together with the description, serve to explain the principles of the application.

[0039] Figure 1 is a flowchart of the far-field noise prediction method of the multi-formation train provided by the application;

[0040] Figure 2 is a top view of the multi-formation train provided by the application;

[0041] Figure 3 is another flowchart of the far-field noise prediction method of the multi-formation train provided by the application;

[0042] Figure 4 is a sound pressure spectrum curve diagram of measuring points corresponding to two cars in a four-formation train;

[0043] Figure 5 is a sound pressure spectrum curve diagram of measuring points corresponding to three cars in a five-formation train;

[0044] Figure 6 is a sound pressure spectrum curve diagram of measuring points corresponding to four cars in a six-formation train;

[0045] Figure 7 is a schematic diagram of positions of a single car and a sound receiving point;

[0046] Figure 8 is a curve diagram of a relationship between sound pressure levels of the sound receiving point and formation numbers;

[0047] Figure 9 is a schematic diagram of a far-field sound receiving point arrangement position;

[0048] Figure 10are far-field noise spatial distribution maps under different marshalling numbers. DETAILED DESCRIPTION

[0049] Various exemplary embodiments of the present application will now be described in detail with reference to the accompanying drawings. It should be noted that the relative arrangement of components and steps, numerical expressions, and numerical values set forth in these embodiments are not limiting to the scope of the present application unless specifically stated otherwise.

[0050] The following description of at least one exemplary embodiment is merely exemplary in nature and is in no way intended to limit the scope of the application its application or uses.

[0051] Techniques, methods, and apparatus known to those of ordinary skill in the relevant art can not be discussed in detail herein. However, where appropriate, such techniques, methods, and apparatus should be considered as being part of the specification.

[0052] In all of the examples shown and discussed herein, any specific values should be interpreted as merely exemplary and not as a limitation. Thus, other examples of exemplary embodiments can have different values.

[0053] It should be noted that like reference numerals and letters refer to like items in the following drawings, and thus, once an item is defined in one drawing, it need not be discussed further in subsequent drawings.

[0054] Embodiment 1

[0055] In combination Figure 1 and Figure 2 A specific embodiment of the method for predicting far-field noise of a multi-marshalling train provided by the present application is described, which includes:

[0056] S101: Establishing a multi-marshalling train model, the multi-marshalling train model including a head car, intermediate cars, and a tail car arranged in sequence, the intermediate cars including at least one car;

[0057] In step S101, the multi-marshalling train model is a smooth car body, and components such as air conditioners, windshields, and pantographs are ignored, which is a preparation for step S102 to avoid the problem of slightly large noise source intensity caused by the pantograph above the car.

[0058] S102: Setting the head car, the car, and the tail car as line sound sources with the same sound power, and ignoring the influence of the speciality of the streamlined shape of the head car and the tail car;

[0059] S103: Setting a sound receiving point, the sound receiving point being located on one side of the multi-marshalling train model and having a spacing with the multi-marshalling train model, the line connecting the sound receiving point and the center point of the multi-marshalling train model being perpendicular to the running direction of the multi-marshalling train model, and the noise sound pressure intensity of the sound receiving point being calculated according to the following method:

[0060]

[0061] wherein, L p is the noise sound pressure intensity of the sound receiving point, p0 2 is the reference sound pressure square, generally 20 micro-pascal, p 2 is the sound pressure square generated by the multi-formation train model at the sound receiving point, A is a constant, and N is the formation number of the multi-formation train model.

[0062] wherein, Q is the sound receiving point, the noise sound pressure intensity of the sound receiving point is calculated, and finally the relationship between the noise sound pressure intensity of the sound receiving point and the formation number of the multi-formation train model is obtained, so that the purpose of predicting the noise sound pressure intensity of the sound receiving point through the formation number of the multi-formation train model is achieved.

[0063] The following Figure 2 , Figure 3 , Figure 4 , Figure 5 , Figure 6 , Figure 7 , Figure 8 , Figure 9 and Figure 10 Another specific embodiment of the multi-formation train far-field noise prediction method provided by the application is described.

[0064] Embodiment 2

[0065] This is another specific embodiment of the multi-formation train far-field noise prediction method provided by the application, which comprises:

[0066] S201: Establishing a multi-formation train model, the multi-formation train model comprising a head car, an intermediate car and a tail car arranged in sequence, and the intermediate car can comprise at least one car compartment;

[0067] In step S201, the multi-formation train model takes the Beijing-Shanghai CRH380A type high-speed train as an example, the car body is smooth, and components such as air conditioners, windshields and pantographs are ignored, so as to lay the foundation for step S202 and avoid the problem that the noise source intensity is slightly large due to the pantograph existing above the car compartment, thereby facilitating the investigation of the influence of the formation number on the near-field noise.

[0068] S202: Setting a measuring point at the center position of the top of each car compartment, respectively acquiring the sound pressure spectrum curve corresponding to each measuring point, and judging whether the sound pressure spectrum curve corresponding to each measuring point is coincident or not; if there is coincidence, the sound power of all car compartments is the same.

[0069] In step S202, the number of the head car and the tail car of the multi-formation train with different formation numbers is fixed, and only the number of the car compartments of the intermediate car changes, and the car compartment of the intermediate car is the most relevant to the formation.

[0070] Specifically, steady-state RANS calculations were performed, with the inlet flow velocity set at 300 km / h. Assuming the train was stationary, the ground was considered a moving wall, and its speed was the same as the inlet flow velocity. Characteristic boundary conditions were set at the far-field boundary, and the outlet was a pressure outlet with a pressure of 1 standard atmosphere. The inlet flow temperature was assumed to be 288.15 K, and viscosity and temperature satisfied Sutherland's law. For NLAS aerodynamic noise calculations, the inlet, far-field, and outlet boundaries were set as NLAS outer-field boundaries, and absorption layers were installed at these three locations to prevent sound wave reflection from contaminating the internal flow field. The Fourier series term was set to 200 for more accurate reconstruction of the subgrid source terms during turbulent fluctuation reconstruction. The NLAS time step was set to 1 × 10⁻⁶. -4 The total number of calculation steps is set to 20,000, and the total physical time of the simulation is 2 seconds. This allows for relatively accurate capture of noise sound pressure levels within the frequency range of 10 to 10,000 Hz.

[0071] Reference Figure 4 , Figure 4 The image shows the sound pressure spectrum curves corresponding to the measuring points of two carriages in a four-car train. It can be seen that the sound pressure spectrum curves corresponding to the measuring points of the two carriages are very similar, and their A-weighted total sound pressure levels are both around 117 dBA. This indicates that, under the condition of a smooth train body and ignoring components such as air conditioning, windshields, and pantographs, it is reasonable for the sound pressure intensities of different carriages to be similar.

[0072] Reference Figure 5 and Figure 6 , Figure 5 This is a sound pressure spectrum curve corresponding to the measuring points in three carriages of a five-car train. Figure 6 This is a sound pressure spectrum curve of the measurement points in four carriages of a six-car train. It can be seen that in different multi-car train models, the sound pressure spectrum curves of the measurement points in each middle car are generally similar, with slight differences in the low-frequency range. The A-weighted total sound pressure level at each measurement point is also relatively similar, with a difference of no more than 2 dBA. Specifically, the average A-weighted total sound pressure level at each measurement point in the five-car train model is approximately 115 dBA, while in the multi-car train model it is approximately 117 dBA.

[0073] Although the sound pressure levels of the carriages in different multi-car train models differ, the overall amplitude difference is small, and the difference between the measuring points in each carriage is also small. Therefore, it can be assumed that the sound pressure intensity between different carriages is similar, which makes it easier to simplify the model and facilitates subsequent analysis of the relationship between the sound pressure level and the number of carriages in multi-car trains.

[0074] S203: Set the lead car, carriages and tail car as line sound sources with the same sound power, so that the influence of the special streamline shape of the lead car and tail car can be ignored;

[0075] In step S203, it is assumed that all the cars are consistent, i.e. the sound power of each car is consistent. Each car is regarded as a line sound source, and adjacent line sound sources are connected end to end. In addition, since the head car and the tail car, which are important noise sources of the train, do not change with the number of marshalling, the noise source intensity thereof is also assumed, and the sound power thereof is assumed to be the same as that of the car, so that the multi-marshalling train is transformed into a plurality of line sound sources with the same intensity.

[0076] S204: setting a sound receiving point, the sound receiving point being located on one side of the multi-marshalling train model and having a spacing from the multi-marshalling train model, the line connecting the sound receiving point and the center point of the multi-marshalling train model being perpendicular to the running direction of the multi-marshalling train model, and the noise sound pressure intensity of the sound receiving point being calculated according to the following method:

[0077]

[0078] wherein L p is the noise sound pressure intensity of the sound receiving point, p0 2 is the reference sound pressure square, p 2 is the sound pressure square generated by the multi-marshalling train model at the sound receiving point, A is a constant, N is the number of marshalling of the multi-marshalling train model, ω0 is the reference sound power, ρ is the air density, c is the air speed, and ω1 is the sound power per unit length of a single car.

[0079] By calculating the noise sound pressure intensity of the sound receiving point, the relationship between the noise sound pressure intensity of the sound receiving point and the number of marshalling of the multi-marshalling train model is finally obtained, so as to achieve the purpose of predicting the noise sound pressure intensity of the sound receiving point through the number of marshalling of the multi-marshalling train model.

[0080] In step S204, the calculation method of the noise sound pressure intensity of the sound receiving point is obtained according to the following steps:

[0081] It can be found from the near-field noise spectrum that the near-field noise source of the high-speed train is broadband noise containing multiple frequency components, which are usually mutually incoherent, and their superposition should be the superposition of energy.

[0082] For a point sound source, the mean square sound pressure of the point sound source is calculated according to the following method:

[0083]

[0084] wherein p1 2 is the mean square sound pressure of the point sound source, ω is the sound power of the point sound source, ρ is the air density, c is the air speed, and r i is the distance between the point sound source and the sound receiving point.

[0085] Since the line sound source can be regarded as the superposition of point sound sources along a straight line, for incoherent point sound sources, the square of the sound pressure generated by them at the receiving point is the sum of the squares of the sound pressures generated by each of them. The aerodynamic noise of a multi-formation train is distributed over the entire length of the train and contains various frequency components, so the noise at each point source can be treated as incoherent.

[0086] The square of the sound pressure generated by a single car at the receiving point p i 2 , comprising:

[0087] Referring to Figure 7 , Figure 7 is a schematic view of the position of a single car and a receiving point Q, in the direction from the tail car to the head car, the single car including opposite first and second ends, the length of the single car being D, the sound power per unit length of the single car being ω1, the sound power corresponding to a length dx being ω1dx, dx being taken as infinitely small, so that it can be regarded as a point source, the square of the sound pressure generated by the point source at the receiving point being calculated according to the following method:

[0088]

[0089] wherein d(p1 2 ) is the differential value of the square of the sound pressure generated by the point source at the receiving point, d is a differential symbol, ρ is the air density, c is the air speed, ω1 is the sound power per unit length of the single car, r is the vertical distance between the receiving point and the single car, θ1 is the angle formed by the direction of the receiving point pointing to the first end and being perpendicular to the running direction of the multi-formation train model, and θ2 is the angle formed by the direction of the receiving point pointing to the second end and being perpendicular to the running direction of the multi-formation train model.

[0090] It can be understood that, according to the derivation of the above formula, the square of the sound pressure generated by the single car at the receiving point p i 2 is calculated according to the following method:

[0091]

[0092] wherein p i 2 is the square of the sound pressure generated by the single car at the receiving point, ρ is the air density, c is the air speed, ω1 is the sound power per unit length of the single car, r is the vertical distance between the receiving point and the single car, θ1 is the angle formed by the direction of the receiving point pointing to the first end and being perpendicular to the running direction of the multi-formation train model, and θ2 is the angle formed by the direction of the receiving point pointing to the second end and being perpendicular to the running direction of the multi-formation train model.

[0093] The sound pressure square p 2 The calculation is performed according to the following method:

[0094]

[0095] Wherein, p 2 is the sound pressure square generated by the multi-formation train model at the sound receiving point, N is the formation number of the multi-formation train model, p i 2 is the sound pressure square generated by the single car at the sound receiving point, +N / 2 is the multi-formation train model located in the interval from the end of the head car away from the tail car to the center point of the multi-formation train model, and -N / 2 is the multi-formation train model located in the interval from the end of the tail car away from the head car to the center point of the multi-formation train model.

[0096] In step S204, the angle formed by the sound receiving point and the multi-formation train model is also calculated, and the calculation is performed according to the following method:

[0097] According to the ISO-2005-3095 standard, the vertical distance between the sound receiving point and the multi-formation train model is 25 meters, and the length of the single car is 25 meters;

[0098]

[0099] Wherein, N is the formation number of the multi-formation train model, θ1 is the angle formed by the direction of the sound receiving point pointing to the first end and being perpendicular to the running direction of the multi-formation train model, and θ2 is the angle formed by the direction of the sound receiving point pointing to the second end and being perpendicular to the running direction of the multi-formation train model.

[0100] Since the vertical distance between the sound receiving point and the multi-formation train model is set to 25 meters, and the length of the single car is 25 meters, the angle formed by the sound receiving point and the multi-formation train model can be related to the formation number, and the noise sound pressure intensity of the sound receiving point can be calculated by substituting, and finally the relationship between the noise sound pressure intensity of the sound receiving point and the formation number is obtained.

[0101] In the embodiment of the application, the far-field noise of the single car is first solved, and then the change rule of the multi-formation train noise is analyzed, and the far-field noise of the multi-formation train is inversely deduced from the noise intensity of the single car.

[0102] Referring to Figure 8 , Figure 8 is a relationship curve between the sound pressure level of the sound receiving point and the formation number, and the noise sound pressure intensity of the sound receiving point increases with the increase of the formation number of the multi-formation train model, but the slope decreases with the increase of the formation number of the multi-formation train model.

[0103] When the formation number of the multi-formation train model increases to the limit value, the noise sound pressure intensity of the sound receiving point remains unchanged.

[0104] It can be understood that when the number of marshalling is increased from 4 to 16, the sound pressure level of the sound point is increased by about 2.7dB. Since the sound point is located in the middle of the multi-marshalling train model, the position of the sound point is the largest angle of the multi-marshalling train model, and the sound pressure level increase brought by this is also the largest. If other sound point positions are considered, the sound pressure level increase will be reduced.

[0105] In some optional embodiments, the number of marshalling of the multi-marshalling train model N≥3, when the number of marshalling is 3, the multi-marshalling train model includes a head car, a tail car and a car, and the far-field noise can also be predicted by the method provided by the application.

[0106] It can be understood that after the near-field noise is calculated, the far-field noise point noise can be solved by the FW-H equation. Referring to Figure 9 , Figure 9 is a schematic view of the arrangement position of the far-field sound point. The far-field noise sound point is selected according to the requirement of ISO-2005-3095, and in order to investigate the spatial distribution of the train far-field noise along the x direction, the point on the line 25 meters away from the center of the train track and 3.5 meters high is selected.

[0107] Referring to Figure 10 , Figure 10 is a spatial distribution diagram of far-field noise under different marshalling numbers. The following will be combined with Figure 9 Only the spatial distribution of the far-field point noise intensity of the high-speed train with 4 marshalling and 6 marshalling is analyzed.

[0108] It can be seen that the spatial distribution of the far-field noise of the high-speed train under different marshalling numbers is very close, and under the same position condition, the intensity value of the sound point of 4 marshalling is slightly lower than that of the sound point of 6 marshalling. This is consistent with the discussion of the single-point noise intensity changing with the number of marshalling. The far-field continuous A-weighted sound pressure level can be obtained by calculating the above sound point noise value. Among them, the sound pressure level corresponding to the 4 marshalling train is about 89.15dBA, and the sound pressure level corresponding to the 6 marshalling train is about 89.94dBA, and the difference between the two is 0.79dB. And from Figure 9It can be seen that the sound pressure level intensity of the 4-formation and 6-formation is about 0.42dB, which is close to the actual calculation value, but still has a certain deviation. The deviation is derived from the following aspects: on the one hand, the sound source intensity value of the head and tail car flow lines is different from that of the middle car; on the other hand, the noise distribution on the car of the middle car is also different from that of the completely uniform intensity line sound source, but the difference is very small, which will not affect the rationality and accuracy of the far-field noise prediction method of the multi-formation train provided in the embodiment. In the embodiment, the head car, the car and the tail car are set as the line sound sources with the same sound power, and the influence of the formation number on the far-field noise of the train can be roughly estimated by the formula. When the high-speed train increases from 4 formations to 16 formations, the far-field continuous A-weighted sound pressure level increases by about 1dB. Thus, under the existing calculation conditions, because it is difficult to accurately calculate the noise intensity of the long formation, the far-field noise characteristics of the multi-formation train can be predicted by the far-field noise prediction method of the multi-formation train provided in the embodiment.

[0109] It can be seen from the above embodiment that the far-field noise prediction method of the multi-formation train provided in the embodiment at least achieves the following beneficial effects:

[0110] In the far-field noise prediction method of the multi-formation train provided in the embodiment, the head car, the car and the tail car are set as the line sound sources with the same sound power, the problem of slightly larger noise source intensity caused by the pantograph existing above the car is ignored, and the influence of the speciality of the head car and the tail car flow lines is also ignored. The noise sound pressure intensity of the sound receiving point is calculated, and finally the relationship between the noise sound pressure intensity of the sound receiving point and the formation number of the multi-formation train model is obtained, so as to achieve the purpose of predicting the noise sound pressure intensity of the sound receiving point through the formation number of the multi-formation train model.

[0111] Although some specific embodiments of the present application have been described in detail through examples, those skilled in the art should understand that the above examples are only for illustration, but not for limiting the scope of the present application. Those skilled in the art should understand that the above embodiments can be modified without departing from the scope and spirit of the present application. The scope of the present application is defined by the appended claims.

Claims

1. A method of far-field noise prediction for a multi- consist train, the method comprising: The method comprises the following steps: establishing a multi-formation train model, the model comprising a head car, a middle car and a tail car arranged in sequence, the middle car comprising at least one car; setting the head car, the car and the tail car as linear sound sources with the same sound power; setting a sound receiving point, the point being located on one side of the model and having a distance to the model, the line connecting the point and the center of the model being perpendicular to the running direction of the model, and the noise sound pressure intensity of the point being calculated according to the following method: Wherein, L p is the noise sound pressure intensity of the sound receiving point, p0 2 is the reference sound pressure square, p 2 is the sound pressure square generated by the multi-formation train model at the sound receiving point, A is a constant, and N is the formation number of the multi-formation train model; The multiple unit train model generates a sound pressure square p at the sound receiving point 2 The calculation is performed according to the following method: where p i 2 is the sound pressure square generated by the single section of the car at the sound receiving point, +N / 2 is the multiple unit train model located in the interval from the end of the head car away from the tail car to the center point of the multiple unit train model, and -N / 2 is the multiple unit train model located in the interval from the end of the tail car away from the head car to the center point of the multiple unit train model.

2. The method of far-field noise prediction for a multi -unit train of claim 1, wherein, In a direction of the head car from the tail car, the single car includes opposite first and second ends, the single car producing a sound pressure square p i 2 The calculation is made according to the following method: wherein, ρ is the air density, c is the air speed, ω1 is the sound power per unit length of the car, r is the vertical distance between the point and the car, θ1 is the angle between the direction of the point to the first end and the line perpendicular to the running direction of the model, and θ2 is the angle between the direction of the point to the second end and the line perpendicular to the running direction of the model.

3. The method of far-field noise prediction for a multi -unit train of claim 1, wherein, The method further comprises calculating the angle between the point and the model, and calculating the sound power of the car according to the following method: setting the vertical distance between the point and the model as 25 meters, and the length of the car as 25 meters; wherein, θ1 is the angle between the direction of the point to the first end and the line perpendicular to the running direction of the model, θ2 is the angle between the direction of the point to the second end and the line perpendicular to the running direction of the model, +N / 2 is the part of the model from the end of the head car away from the tail car to the center of the model, and -N / 2 is the part of the model from the end of the tail car away from the head car to the center of the model.

4. The method of claim 1, wherein, The method further comprises: setting a measuring point at the center of the top of each car, and obtaining the sound pressure spectrum curve corresponding to each measuring point; judging whether the sound pressure spectrum curves corresponding to each measuring point coincide; if the curves coincide, the sound power of all the cars is the same.

5. The method of claim 2, wherein, calculating a sound pressure square p generated by the car in the sound receiving point i 2 further comprising: setting the length of the car as D, the sound power per unit length of the car as ω1, the sound power of the car with a length of dx as ω1dx, taking dx as infinitely small, and calculating the sound pressure square generated by the point sound source at the point according to the following method: wherein d(p1 2 ) is a differential value of the sound pressure square generated by the point sound source at the sound receiving point, and d is a differential symbol.

6. The method of far-field noise prediction for a multi -unit train of claim 5, wherein, calculating the mean square sound pressure of the point sound source according to the following method: wherein p1 2 is the mean square sound pressure of the point sound source, ω is the sound power of the point sound source, r i is the distance between the point sound source and the sound receiving point.

7. The method of claim 1, wherein, The method further comprises: the noise sound pressure intensity of the point increases with the increase of the formation number of the model, but the slope decreases with the increase of the formation number of the model.

8. The method of far-field noise prediction for a multi -unit train of claim 7, wherein, The method further comprises: when the formation number of the model increases to a limit value, the noise sound pressure intensity of the point remains unchanged.

9. The method of claim 1, wherein, The formation number N of the model is greater than or equal to 3.

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