Optimization method for design scheme of sound field in passenger car

Abstract

The invention discloses a passenger car internal sound field design scheme optimization method comprising the following steps: 1, collecting real car size data, and constructing an urban passenger car model; 2, setting an initial value of a loudspeaker optimization parameter and an initial value of an interior material optimization parameter in the urban bus model, and measuring the sound field unevenness of the whole bus and the signal-to-noise ratio of the whole bus under different frequencies at a plurality of measuring points; step 3, adjusting loudspeaker optimization parameters and interior material optimization parameters according to the unevenness of the sound field of the whole vehicle and the signal-to-noise ratio of the whole vehicle to obtain optimal loudspeaker optimization parameters and optimal interior material optimization parameters; and when the sound field unevenness of the whole vehicle is minimum and the signal-to-noise ratio of the whole vehicle is highest, the loudspeaker optimization parameter and the interior material optimization parameter are optimal. The method has the advantages that in-vehicle sound balance and consistency are improved, and environmental interference is reduced.

Description

Technical Field

[0001] The present invention relates to the field of automobile technology, and more particularly to a method for optimizing a design scheme for an interior sound field of a passenger car. Background Art

[0002] With the continuous improvement of living standards, people's requirements for vehicle quality are getting higher and higher. At present, vehicle noise has become a source of environmental pollution that cannot be ignored. It not only pollutes the riding environment of passengers in the car, but also causes serious pollution to the surrounding environment where the vehicle passes. The level of noise in the car is also an important basis for measuring the riding comfort of the vehicle, which in turn affects the quality of the vehicle.

[0003] Previously, researchers in the field of automotive sound quality often focused on controlling and improving the acoustic environment inside passenger cars. Relatively speaking, city buses have more passengers and a more complex internal sound environment. Focusing on social needs, people have a special and urgent need to improve the sound quality inside city buses.

[0004] For buses, a reasonable bus interior sound field design is the prerequisite for achieving spatial sound field control and improving the sound quality inside the car. The components of the bus interior sound field design will have an impact on the above-mentioned problems. If actual vehicle measurements are used and multiple schemes are enumerated for comparison, it will be time-consuming and labor-intensive and not conducive to the subsequent optimization of the scheme. Therefore, it is very important to use relevant acoustic simulation software, build a sound field control model, refer to the conventional sound field design scheme of the actual vehicle, and make appropriate adjustments to obtain a better in-car sound field environment.

[0005] The current simulation methods used to study the sound field of a mobile and enclosed vehicle interior focus more on basic sound propagation and reflection simulation. Most of them cannot accurately customize the behavior of the speaker and usually lack the flexibility to adjust the speaker characteristics, which limits the accuracy of the simulation and the breadth of application. They cannot adapt to the impact of complex interior materials and changing spatial layouts on the sound field, resulting in deviations between the simulation results and the actual situation. Summary of the invention

[0006] The purpose of the present invention is to design and develop an optimization method for the interior sound field design of a bus. Starting from the selection and arrangement of the speakers in the car, the selection and laying method of the interior decoration materials, and taking the optimization simulation of acoustic performance as the main goal, the interior speakers and interior decoration layout are acoustically comprehensively optimized, thereby improving the balance and consistency of the sound in the car and reducing environmental interference.

[0007] The technical solution provided by the present invention is:

[0008] A method for optimizing a bus interior sound field design scheme comprises the following steps:

[0009] Step 1: Collect real vehicle size data and build a city bus model;

[0010] Step 2: setting initial values ​​of speaker optimization parameters and initial values ​​of interior material optimization parameters in the city bus model, and measuring the vehicle sound field non-uniformity and vehicle signal-to-noise ratio at different frequencies at multiple measurement points;

[0011] Step 3: adjusting the speaker optimization parameters and the interior material optimization parameters according to the sound field non-uniformity of the whole vehicle and the signal-to-noise ratio of the whole vehicle to obtain the optimal speaker optimization parameters and the interior material optimization parameters;

[0012] Among them, when the sound field unevenness of the whole vehicle is the smallest and the signal-to-noise ratio of the whole vehicle is the highest, the speaker optimization parameters and interior material optimization parameters are optimal.

[0013] Preferably, in the step 1, a city bus model is constructed by using COMSOL Multiphysics.

[0014] Preferably, the optimization parameters of the speaker include:

[0015] The incident pressure field amplitude of the loudspeaker sound source, the arrangement of the loudspeakers and the number of loudspeakers.

[0016] Preferably, the interior material optimization parameters include:

[0017] The material of interior materials, the properties of interior materials and the laying method of interior materials.

[0018] Preferably, the multiple measuring points are respectively arranged at the right ear of a sitting driver, the right ears of passengers in different passenger areas, and the right ears of passengers in different passenger areas, and the number of the measuring points is 11.

[0019] Preferably, the step 2 further comprises:

[0020] The city bus model is divided into grids, and each grid accommodates at least six sound wave wavelengths.

[0021] Preferably, the different frequencies include 125 Hz, 250 Hz, 500 Hz, 1000 Hz, 2000 Hz and 4000 Hz.

[0022] Preferably, the calculation formula for the non-uniformity of the whole vehicle sound field is:

[0023] ΔP max =P max -P min ;

[0024] Where ΔP max is the sound field unevenness, P maxis the maximum sound pressure level simulation value in the listening area of ​​the car, P min It is the minimum sound pressure level simulation value in the listening area of ​​the car.

[0025] Preferably, the calculation formula of the vehicle signal-to-noise ratio is:

[0026]

[0027] Δ=Lp y -Lp n ;

[0028] Where SNR is the signal-to-noise ratio, p s is the sound pressure of signal s, p n is the sound pressure of the background noise n, Δ is the difference between the sound pressure level of the noisy signal and the sound pressure level of the background noise, Lp y is the sound pressure level of the noisy signal y, Lp n is the sound pressure level of background noise n.

[0029] The beneficial effects of the present invention are:

[0030] The present invention designs and develops an optimization method for a bus interior sound field design scheme. Taking a city bus as a research object, the COMSOL Multiphysics software is used to complete the simulation of the bus interior sound field. Starting from the selection and arrangement of the bus interior speakers, the selection and laying method of the interior decoration materials, etc., the optimization simulation of acoustic performance is taken as the main goal, and the acoustic comprehensive optimization design of the sound field related factors such as the bus interior speakers and the interior decoration arrangement is performed, which significantly improves the accuracy and applicability of the simulation, provides relevant suggestions for the production and manufacturing of the bus, improves the balance and consistency of the sound at different positions, helps to improve the speech clarity and reduce interference, can improve production efficiency, reduce production costs, not only makes up for the deficiencies of the existing technology, but also provides higher flexibility and optimization potential for the bus interior acoustic design. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 The figure is a flow chart of the optimization method of the interior sound field design scheme of a bus according to the present invention.

[0032] Figure 2 It is a schematic diagram of the frequency response curve of the plane wave radiation axis 1 meter set in the COMSOL software in the embodiment of the present invention.

[0033] Figure 3 It is a structural diagram of the initial values ​​of the speaker arrangement and the initial values ​​of the number of speakers in the embodiment of the present invention.

[0034] Figure 4 Schematic diagram of optimization parameter types for interior materials in the embodiment of the present invention.

[0035] Figure 5 Schematic diagram of the sound absorption coefficients of various interior materials at different frequencies in the embodiment of the present invention.

[0036] Figure 6 Schematic diagram of the positions of multiple measuring points in the embodiment of the present invention.

[0037] Figure 7 Schematic diagram of the side view of the position of the sitting posture measurement points in the embodiment of the present invention.

[0038] Figure 8 Schematic diagram of the top view of the position of the sitting posture measurement points in the embodiment of the present invention.

[0039] Fig. 9 Schematic diagram of the sound pressure level curve of the measuring points of the symmetrical arrangement scheme in the embodiment of the present invention.

[0040] Fig.10 Schematic diagram of the comparison of the unevenness of the whole vehicle sound field in different speaker arrangements in the embodiment of the present invention.

[0041] Fig.11 It is a schematic diagram of the sound pressure level broken line at each measuring point when the loudspeakers are equally spaced in the embodiment of the present invention.

[0042] Fig.12 Schematic diagram of the comparison of vehicle signal-to-noise ratios for different speaker arrangements in the embodiment of the present invention.

[0043] Fig.13 Comparison of the signal-to-noise ratio of the sound field in the car before and after the speakers are aligned.

[0044] Fig.14 Schematic diagram of the optimal loudspeaker arrangement scheme in the embodiment of the present invention.

[0045] Fig.15 Schematic diagram of the arrangement of the in-vehicle sound field of four speakers in the embodiment of the present invention.

[0046] Fig.16 Schematic diagram of the arrangement of the in-vehicle sound field of five speakers in the embodiment of the present invention.

[0047] Fig.17 Schematic diagram of the arrangement of the in-vehicle sound field of nine speakers in the embodiment of the present invention.

[0048] Fig.18 Schematic diagram of the arrangement of the in-vehicle sound field of 12 speakers in the embodiment of the present invention.

[0049] Fig.19 It is a line graph of the sound pressure level at each measuring point simulated under the four speaker solutions in the embodiment of the present invention.

[0050] Fig. 20 It is a schematic diagram of the comparison of the preliminary selection schemes of the sound field unevenness at each frequency for different numbers of loudspeakers in the embodiment of the present invention.

[0051] Fig.21 Schematic diagram of the comparison between the signal-to-noise ratio of the in-vehicle sound field of different numbers of speakers in the embodiment of the present invention and the preliminary solution.

[0052] Fig. 22 It is a line graph of the sound pressure level at each measuring point simulated under the five speaker solutions in the embodiment of the present invention.

[0053] Fig.23 It is a line graph of the sound pressure level at each measuring point simulated under 9 speaker solutions in the embodiment of the present invention.

[0054] Fig.24 It is a line graph of the sound pressure level at each measuring point simulated under the 12 speaker solutions in the embodiment of the present invention.

[0055] Fig.25 It is a line graph of the sound pressure levels at each measuring point when the incident pressure field intensity of the rear speaker is 0.45 Pa in the embodiment of the present invention.

[0056] Fig.26 It is a line graph of the sound pressure levels at various measuring points when the incident pressure field intensity of the rear speaker is 0.55 Pa in the embodiment of the present invention.

[0057] Fig. 27 It is a schematic diagram comparing the sound field non-uniformity at each frequency after the incident pressure field is adjusted in the embodiment of the present invention with the simulation results of the preliminary selection scheme.

[0058] Fig.28 It is a schematic diagram comparing the signal-to-noise ratio of the sound field in the vehicle after the incident pressure field is adjusted in the embodiment of the present invention with that of the preliminary selection scheme.

[0059] Fig.29 This is a line graph of the sound pressure levels at each measuring point in scheme 1 of the embodiment of the present invention.

[0060] Fig.30 It is a line graph of the sound pressure levels at each measuring point in scheme 2 of the embodiment of the present invention.

[0061] Fig.31 It is a line graph of the sound pressure levels at each measuring point in scheme three of the embodiment of the present invention.

[0062] Fig.32 This is a line graph of the sound pressure levels at each measuring point in scheme 4 of the embodiment of the present invention.

[0063] Fig.33This is a line graph of the sound pressure levels at each measuring point in scheme five of the embodiment of the present invention.

[0064] Fig.34 This is a line graph of the sound pressure levels at each measuring point in scheme six of the embodiment of the present invention.

[0065] Fig.35 It is a schematic diagram comparing the sound field non-uniformity at each frequency after the incident pressure field of Schemes 1 to 8 is adjusted in the embodiments of the present invention with the simulation results of the preliminary scheme.

[0066] Fig.36 It is a schematic diagram of the comparison between the signal-to-noise ratio of the sound field in the vehicle after the incident pressure field is adjusted in schemes 1 to 8 in the embodiments of the present invention and the preliminary scheme.

[0067] Fig.37 It is a schematic diagram of the signal-to-noise ratio of the simulated in-vehicle sound field under different interior materials and layout schemes in the embodiment of the present invention.

[0068] Fig.38 Schematic diagram of a comprehensive preferred arrangement of speakers in the embodiment of the present invention.

[0069] Fig.39 Schematic diagram of the total sound pressure levels corresponding to different frequencies at various measuring points in the comprehensive optimal arrangement of loudspeakers in the embodiment of the present invention.

[0070] Fig.40 Schematic diagram of the comparison of the signal-to-noise ratio of the in-vehicle sound field of the comprehensive optimal speaker arrangement scheme in the embodiment of the present invention and the preliminary selection scheme.

[0071] Fig.41 It is a schematic diagram comparing the sound field unevenness at various frequencies of the comprehensive optimal arrangement scheme of speakers in the embodiment of the present invention with that of the preliminary selection scheme.

[0072] Fig.42 Schematic diagram of the plane sound pressure level of the front row sitting posture before optimization in the embodiment of the present invention.

[0073] Fig.43 This is a schematic diagram of the plane sound pressure level of the front row standing posture before optimization in the embodiment of the present invention.

[0074] Fig.44 Schematic diagram of optimizing the plane sound pressure level of the front and rear row seating postures in the embodiment of the present invention.

[0075] Fig.45 Schematic diagram of optimizing the plane sound pressure level of the front and rear row standing postures in the embodiment of the present invention.

[0076] Fig.46 Schematic diagram of the plane sound pressure level of the front row sitting posture after optimization in the embodiment of the present invention.

[0077] Fig.47 Schematic diagram of the plane sound pressure level of the front row standing posture after optimization in the embodiment of the present invention.

[0078] Fig.48 Schematic diagram of the plane sound pressure level of the rear-seat posture after optimization in the embodiment of the present invention.

[0079] Fig.49 Schematic diagram of the plane sound pressure level of the rear row standing posture after optimization in the embodiment of the present invention. DETAILED DESCRIPTION

[0080] The present invention is further described in detail below so that those skilled in the art can implement it according to the description.

[0081] like Figure 1 As shown, the optimization method of the bus interior sound field design provided by the present invention specifically includes the following steps:

[0082] Step 1: Collect the measured internal dimension data of the city bus and build a city bus model;

[0083] Step 2: setting initial values ​​of speaker optimization parameters and initial values ​​of interior material optimization parameters in the city bus model, meshing the overall simulation model and performing finite element analysis, setting multiple measurement points in various locations in the vehicle, taking the whole vehicle sound field unevenness and the whole vehicle signal-to-noise ratio as evaluation indicators, and obtaining the whole vehicle sound field unevenness and the whole vehicle signal-to-noise ratio at different frequencies at multiple measurement points;

[0084] The speaker optimization parameters include: the incident pressure field amplitude of the speaker sound source, the speaker arrangement mode and the number of speakers;

[0085] The interior material optimization parameters include: the material of the interior material, the arrangement of the interior material, and the laying method of the interior material.

[0086] The multiple measuring points are respectively arranged at the right ear of a driver in a sitting position, the right ears of passengers in different passenger zones in a sitting position, and the right ears of passengers in different passenger zones in a standing position.

[0087] Step 3: adjusting the speaker optimization parameters and the interior material optimization parameters according to the vehicle sound field non-uniformity and the vehicle signal-to-noise ratio to obtain the optimal speaker optimization parameters and the optimal interior material optimization parameters;

[0088] Among them, when the sound field unevenness is the smallest and the signal-to-noise ratio is the highest, this is the time for the optimal speaker optimization parameters and the optimal interior material optimization parameters.

[0089] Example

[0090] Step 1: Collect the measured internal dimension data of ordinary city buses in operation in Changchun, and use the acoustic design software COMSOL Multiphysics 6.1 to build a city bus model. This is because COMSOL Multiphysics 6.1 software can realize professional sound field simulation of on-board speakers and can be interconnected with Matlab. Therefore, this software is selected for in-car sound field simulation in this embodiment.

[0091] When building a city bus model in COMSOL, the three-dimensional space dimension is selected to represent the interior of the vehicle. This model includes the internal structures such as the dashboard, windows, doors, rear storage table and seats in detail, while ignoring the thickness of the outer wall of the car to simplify the model complexity. This design is mainly to optimize the sound field inside the vehicle. The space inside the car is set as a space entity filled with air. This setting helps to simulate and analyze the acoustic environment inside the car. This bus car model focuses on the internal structure of the vehicle to improve the accuracy and efficiency of the simulation.

[0092] Step 2: setting initial values ​​of speaker optimization parameters and initial values ​​of interior material optimization parameters in the city bus model, meshing the overall simulation model and performing finite element analysis, setting multiple measurement points and their measurement frequency ranges at various locations in the vehicle, and setting the whole vehicle sound field unevenness and the whole vehicle signal-to-noise ratio at different frequencies at multiple measurement points as evaluation indicators, performing model simulation, and obtaining the whole vehicle sound field unevenness and the whole vehicle signal-to-noise ratio at different frequencies at each measurement point;

[0093] In this embodiment, the initial values ​​of the optimization parameters of the speaker include:

[0094] The speaker type is the Swans M5N low-midrange speaker. Since there is no ready-made speaker library in the COMSOL software, in order to reproduce the effect of the Swans M5N low-midrange speaker in the COMSOL software, plane wave radiation is used instead of the Swans M5N low-midrange speaker. By adjusting the pressure amplitude of the incident pressure field, the plane wave produces the same excitation effect as the Swans M5N low-midrange speaker, such as Figure 2 As shown in the figure, the frequency response curve of the plane wave radiation sound source at 1 meter on the axis is compared with the frequency response curve of the Swans M5N low-midrange speaker measured at 1 meter on the axis. The comparison shows that the change trends of the frequency response curves of the two are similar, and the sound pressure level values ​​of the measurement points at the same frequency are also close, which confirms the feasibility of using the plane wave incident pressure field to replace the effect of the Swans M5N low-midrange speaker.

[0095] The interior of a city bus can also be regarded as a closed indoor space. From the perspective of interior acoustics design, the harmony and uniformity of the sound field should be ensured as much as possible, that is, the symmetry of the arrangement of the speakers in the car should be ensured. In addition, from the perspective of interior acoustics design, making full use of direct sound can ensure that the sound fidelity in the listening area is high and is less affected by the external environment. Combining the above reasons and considering the large available space on the roof of a city bus, such as Figure 3 As shown in the figure, the initial value of the speaker arrangement in the model is designed with reference to the actual speaker arrangement scheme inside the bus, including one speaker arranged directly above the driver's seat, two speakers arranged symmetrically in the passenger area at 350 cm from the front windshield of the vehicle and 60 cm from the longitudinal centerline of the vehicle, two speakers arranged symmetrically in the passenger area at 650 cm from the front windshield of the vehicle and 60 cm from the longitudinal centerline of the vehicle, and two speakers arranged symmetrically in the passenger area at 950 cm from the front windshield of the vehicle and 60 cm from the longitudinal centerline of the vehicle, a total of seven Hivi M5N low-midrange speakers, facing vertically downward.

[0096] The interior material optimization parameters include: the material of the interior material, the property of the interior material (sound absorption coefficient) and the laying method of the interior material, such as Figure 4 As shown in the figure, the material texture and properties of each structure in the city bus model at 500Hz are analyzed using COMSOL software.

[0097] After completing the selection and laying of bus materials, the impedance of various interior materials laid in the vehicle is set in the COMSOL software to accurately perform sound field simulation analysis, such as Figure 5 As shown in the figure, the sound absorption coefficient of the material will change at different frequencies. Therefore, the cubic spline interpolation function in the COMSOL software is called using the data in the figure as the impedance value of various paving materials, so that the impedance value of the model material can change accordingly with the frequency.

[0098] In this embodiment, 11 measurement points are selected inside the bus to simulate the sound pressure level inside the bus, such as Figure 6As shown, measuring point 1 in the driving area is at the right ear of the driver's sitting position, measuring point 2 is located at the right ear of the second seat on the left side of the passenger area, measuring point 3 is located at the right ear of the second seat on the left side of the passenger area, measuring point 4 is located at the right ear of the fourth seat on the left side of the passenger area, measuring point 5 is located at the right ear of the first aisle seat on the left side of the rear area of ​​the passenger area, and measuring point 6 is located at the right ear of the fourth window seat on the left side of the rear area of ​​the passenger area. Measuring point 7 is located at the right ear of the passenger sitting in the center of the last row of seats in the passenger area. Measuring point 8 is located at the right ear of the passenger standing in the middle of the third and fourth seats in the rear passenger area. Measuring point 9 is located at the right ear of the passenger standing at the rear door of the bus. Measuring point 10 is located at the right ear of the passenger standing in the middle of the second seat on the right side of the passenger area. Measuring point 11 is located at the right ear of the second seat on the right side of the passenger area. It is approximately on the central axis of the bus and is 160 cm above the floor. Figure 7 , Figure 8 As shown, the specific location of each measuring point is set in accordance with the sitting measurement point setting specified in GB / T25982-2010.

[0099] To ensure the accuracy of the simulation, each grid is required to accommodate at least six sound wave wavelengths during grid division, so as to accurately capture the propagation of sound waves in the car. Taking into account the high complexity of the computational model and in order to match the auditory frequency range of the human ear and the limitations of device memory, six frequency points of 125Hz, 250Hz, 500Hz, 1000Hz, 2000Hz and 4000Hz were selected for sound field simulation. This not only ensures the accuracy of the simulation, but also effectively balances the use of computing resources, making the simulation results both scientific and practical.

[0100] In acoustic analysis, the greater the sound field unevenness, the more uneven the sound field distribution, and the smaller the sound field unevenness, the more uniform the sound field distribution. The calculation formula for the sound field unevenness of the whole vehicle is as follows:

[0101] ΔP max =P max -P min ;

[0102] In the formula, ΔP max is the sound field unevenness, P max is the maximum sound pressure level simulation value in the listening area of ​​the car, P min It is the minimum sound pressure level simulation value in the listening area of ​​the car.

[0103] The sound field uniformity index requires that in the entire sound reinforcement area, the deviation of the average sound pressure value at each location is generally required to be below 10-12dB. The sound field unevenness at each frequency can be calculated by the formula and a sound field unevenness graph can be drawn.

[0104] The signal-to-noise ratio is used as an indicator to measure the clarity of the loudspeaker broadcast sound. The higher the signal-to-noise ratio, the easier it is to hear the information played by the loudspeaker. The vehicle signal-to-noise ratio can be calculated by the sound pressure level of the noisy signal and the sound pressure level of the background noise, as shown in the following formula:

[0105]

[0106] Δ=Lp y -Lp n ;

[0107] Where SNR is the signal-to-noise ratio, p s is the sound pressure of signal s, p n is the sound pressure of the background noise n, Δ is the difference between the sound pressure level of the noisy signal and the sound pressure level of the background noise, Lp y is the sound pressure level of the noisy signal y, Lp n is the sound pressure level of background noise n.

[0108] During measurement, it can be used to quickly estimate the signal-to-noise ratio, but there is a certain error. When the difference between the sound pressure level of the noisy signal and the sound pressure level of the background noise is greater than 15dB, the error can be basically ignored and the difference can be directly used as the value of the signal-to-noise ratio. When the difference between the sound pressure level of the noisy signal and the sound pressure level of the background noise is not greater than 15dB, it proves that the environmental noise is too large and the data cannot be used.

[0109] According to the national standard, the sound pressure level limit of the in-car noise of urban buses is 78-86dB. Therefore, the pressure field amplitude of the background noise is set to 0.5Pa in the COMSOL software, and the corresponding in-car sound field background noise average value is about 50dB. Limited by the device memory, the 500Hz frequency is the highest frequency that can be accurately calculated. Therefore, in this embodiment, the average value of the background noise sound pressure level of each measuring point at 500Hz is selected as the background noise sound pressure level of the in-car sound field, and the average value of the noisy signal sound pressure level of each measuring point is used as the signal sound pressure level of the in-car sound field. The signal-to-noise ratio of the in-car sound field can be calculated according to the formula. The larger the signal-to-noise ratio, the smaller the noise mixed in the signal and the higher the clarity of the sound. Otherwise, the opposite is true. Therefore, in order to allow passengers to hear the broadcast sound of the speaker more clearly, the signal-to-noise ratio of the in-car sound field should be improved.

[0110] Step 3: Adjust the speaker optimization parameters and interior material optimization parameters according to the vehicle sound field unevenness and the vehicle signal-to-noise ratio to obtain the optimal speaker optimization parameters and the optimal interior material optimization parameters, including:

[0111] When optimizing the speaker layout plan, considering the symmetry of the overall structure of the bus, it can be inferred that symmetrical arrangement of the speakers can improve the uniformity of the sound field and the signal-to-noise ratio in the car. In the preliminary plan, only one speaker is arranged in the driving area, and the speakers arranged on the left and right in the passenger area are not arranged symmetrically. Simulation results show that if a speaker is added to the driving area, or the speakers on the left and right sides are arranged symmetrically relative to the bus compartment, the uniformity of the sound field and the signal-to-noise ratio in the car can be improved.

[0112] like Fig. 9 As shown in Figure 2, COMSOL simulation obtains a line graph of the sound pressure level at 11 measurement points at each frequency after the speakers are symmetrically arranged, as shown in Figure 2. Fig.10 As shown in the figure, the non-uniformity of the whole vehicle sound field at each frequency after the optimization is calculated and compared with the simulation results of the preliminary scheme. It can be seen that the sound field non-uniformity of the symmetrically arranged speakers is slightly increased at frequencies of 125Hz and 500Hz compared with the preliminary scheme, but in general, the overall non-uniformity of the speakers is significantly reduced after the symmetrical arrangement of the speakers. The most obvious decrease in the non-uniformity of the sound field after the symmetrical arrangement relative to the preliminary scheme is 10.08dB at 1000Hz, and the values ​​of the non-uniformity reduction at other frequencies are all greater than 3dB. Therefore, the change in the speaker layout scheme can indeed effectively reduce the non-uniformity of the sound field in the whole vehicle; the speaker arrangement spacing of the preliminary scheme is different. The distance between the speakers in the driving area and the front of the passenger area is 2.3m, which is less than the 3m distance between the front, middle and rear speakers in the passenger area, such as Fig.11 As shown in the figure, on the basis of symmetrical arrangement of the speakers, the simulated sound pressure level line graph of each measuring point is obtained after adjusting the distance between all the speakers to be consistent. It can be seen that after the adjustment of the distance, the overall unevenness of the sound field in the car is reduced to a certain extent. This proves that on the basis of symmetrical arrangement of the speakers, adjusting the distance between the speakers to make their distances the same can further reduce the unevenness of the sound field in the car, so that the difference in sound pressure levels at various locations will not be too large to affect the comfort of the passengers.

[0113] like Fig.12 As shown in the figure, the signal-to-noise ratio of the sound field in the car before and after the symmetrical arrangement of the speakers obtained by COMSOL simulation shows that the symmetrical arrangement of the speakers can not only reduce the unevenness of the sound field in the car, but also improve the signal-to-noise ratio, making the signal transmission clearer and more accurate. Fig.13 As shown in the figure, the signal-to-noise ratio comparison of the sound field in the car before and after the speakers are arranged uniformly, the signal-to-noise ratio is significantly improved by 5.5dB compared to the symmetrical arrangement scheme.

[0114] Based on the above analysis, we can see that Fig.14As shown, the most suitable speaker arrangement is a left-right symmetrical arrangement with the same front-to-back spacing. Compared with the preliminary scheme, the unevenness of the whole vehicle sound field of this preferred scheme is significantly reduced at all frequencies. The most obvious reduction in sound field unevenness is 10.20dB at 1000Hz. The signal-to-noise ratio of the in-vehicle sound field of this preferred scheme is 7.5dB higher than that of the preliminary scheme.

[0115] When optimizing the number of speakers, as the main sound source inside the bus, the number of speakers will directly and significantly affect the uniformity of the sound field. Theoretically, the more speakers there are, the more precise the control of the sound field inside the car. However, the more speakers does not necessarily mean better, because the sound channels of each speaker will affect each other, and each listening position is the superposition of the effects of all speakers at that point, which means that the interaction between speakers is very complex and may interfere with each other, resulting in reduced sound field uniformity. Therefore, the number of speakers should not be too large.

[0116] This embodiment simulates the in-vehicle sound field with four loudspeakers, 4, 5, 9, and 12. The specific arrangement of the loudspeakers is as follows: Fig.15 , 16 As shown in , 17, and 18, the simulated sound pressure level line graphs and the signal-to-noise ratio of the in-car sound field of the four speaker quantity schemes are obtained, and the in-car sound field unevenness and signal-to-noise ratio under the four numbers are compared with the situation of the primary scheme of 7 speakers: Fig.19 , Fig. 22 , Fig.23 , Fig.24 As shown in the figure, the sound pressure level line graphs of each measurement point simulated under 4, 5, 9, and 12 loudspeaker solutions are shown in the figure. Fig. 20 As shown in the figure, the sound field unevenness at each frequency with different numbers of speakers is compared with the preliminary selection scheme. Fig.21 As shown in the figure, the comparison values ​​of the signal-to-noise ratio of the in-car sound field with different numbers of speakers and the initial solution are shown. The comparison shows that the sound field unevenness of the bus with 5 speakers is small at all frequencies, and its signal-to-noise ratio is also the largest among all the schemes with various numbers, with the signal-to-noise ratio increased by 3dB. Compared with the initial solution, the sound field unevenness of the 5 speakers increases slightly at 2000Hz and 4000Hz, but decreases at other frequencies, with the largest decrease at 250Hz, reaching 5.18dB. Considering that the low grid accuracy of 2000Hz and 4000Hz may affect the accuracy of the sound field unevenness, it can be considered that the number of 5 speakers is the optimal solution.

[0117] When optimizing the incident pressure field amplitude of the loudspeaker sound source, there is a platform at the rear of the passenger area of ​​the bus that is 0.67m higher than the front floor, and the passenger's listening position is also shifted upward by 0.67m. Therefore, if the sound pressure level of the loudspeaker at the rear is the same as that at the front, the sound pressure level in the rear listening area may be higher. Fig.25 , 26 As shown in FIG. 1 , by changing the incident pressure field intensity of the rear speaker through COMSOL simulation, the sound pressure level line graphs of each measuring point corresponding to the incident pressure field intensity of the rear speaker being lowered by 0.05Pa and increased by 0.05Pa can be obtained; Fig. 27 As shown in the figure, the comparison between the sound field non-uniformity at each frequency after the incident pressure field is adjusted and the simulation results of the preliminary selection scheme is shown in the figure. Fig.28 As shown in the figure, the comparison values ​​of the signal-to-noise ratio of the in-car sound field obtained by simulation and the initial solution are shown; it can be seen from the table that only changing the amplitude of the incident pressure field of the rear speaker in the passenger area has no obvious effect on the in-car sound field unevenness and the optimization of the signal-to-noise ratio, and the unevenness at most frequencies is actually increased.

[0118] Considering that all the speakers installed inside the bus are a whole system, changing the amplitude of the sound source incident pressure field of several speakers will affect the sound field generated by other speakers. Therefore, this embodiment also considers the influence of the amplitude of the sound source incident pressure field of other speakers except the rear speakers in the passenger area on the sound field inside the car, and changes the amplitude of the sound source incident pressure field of the speakers in the front, middle and rear of the passenger area respectively, increasing or decreasing by 0.05Pa, and a total of the following 6 situations are obtained:

[0119] Solution 1: The pressure amplitude of the speaker in the driving area is 0.5Pa, the pressure amplitude of the speaker in the front passenger area is 0.55Pa, and the pressure amplitude of the speaker in the middle and rear passenger area is 0.45Pa. The sound pressure level line graph of each measuring point is as follows: Fig.29 As shown;

[0120] Solution 2: The pressure amplitude of the speaker in the driving area is 0.5Pa, the pressure amplitude of the speakers in the front and rear of the passenger area is 0.55Pa, and the pressure amplitude of the speaker in the middle of the passenger area is 0.45Pa. The obtained sound pressure level line graph of each measuring point is as follows: Fig.30 As shown;

[0121] Solution 3: The pressure amplitude of the speaker in the driving area is 0.5Pa, the pressure amplitude of the speaker in the front and middle of the passenger area is 0.55Pa, and the pressure amplitude of the speaker in the rear of the passenger area is 0.45Pa. The obtained sound pressure level line graph of each measuring point is as follows: Fig.31 As shown;

[0122] Solution 4: The pressure amplitude of the speaker in the driving area is 0.5Pa, the pressure amplitude of the speaker in the front passenger area is 0.45Pa, and the pressure amplitude of the speaker in the middle and rear passenger area is 0.55Pa. The obtained sound pressure level line graph of each measuring point is as follows: Fig.32 As shown;

[0123] Scheme 5: The pressure amplitude of the speaker in the driving area is 0.5Pa, the pressure amplitude of the speakers in the front and rear of the passenger area is 0.45Pa, and the pressure amplitude of the speaker in the middle of the passenger area is 0.55Pa. The obtained sound pressure level line graph of each measuring point is as follows: Fig.33 As shown;

[0124] Scheme 6: The pressure amplitude of the speaker in the driving area is 0.5Pa, the pressure amplitude of the speaker in the front and middle of the passenger area is 0.45Pa, and the pressure amplitude of the speaker in the rear of the passenger area is 0.55Pa. The obtained sound pressure level line graph of each measuring point is as follows: Fig.34 As shown;

[0125] Option 7: The pressure amplitude of the speaker in the driving area is 0.5Pa, the pressure amplitude of the front and middle speakers in the passenger area is 0.5Pa, and the pressure amplitude of the speaker in the rear passenger area is 0.45Pa.

[0126] Solution 8: The pressure amplitude of the speaker in the driving area is 0.5Pa, the pressure amplitude of the front and middle speakers in the passenger area is 0.5Pa, and the pressure amplitude of the speaker in the rear passenger area is 0.55Pa.

[0127] like Fig.35 As shown, the comparison of the sound field unevenness at each frequency after the incident pressure field of Schemes 1 to 8 is adjusted with the simulation results of the preliminary scheme. The above eight speaker incident pressure amplitude setting schemes are compared, and the eight schemes are ranked according to the number of frequencies at which the unevenness is reduced and the degree of reduction to obtain the following results (from best to worst): Scheme 6> Scheme 4> Scheme 8> Scheme 2> Scheme 5> Scheme 1> Scheme 3> Scheme 7;

[0128] like Fig.36 As shown, the comparison values ​​of the in-vehicle sound field signal-to-noise ratio of schemes 1 to 8 and the initial scheme are shown. By comparing the above eight speaker incident pressure amplitude setting schemes, the eight schemes are ranked according to the signal-to-noise ratio values ​​to obtain the following results (from best to worst): Scheme 3> Scheme 1> Scheme 2> Scheme 7> Scheme 4> Scheme 8> Scheme 6> Scheme 5;

[0129] From the above conclusions, it can be seen that if you want to reduce the unevenness of the sound field, you should refer to the speaker incident pressure amplitude setting plan of Plan 6, lower the incident pressure amplitude of the front and middle speakers in the passenger area, and increase the incident pressure amplitude of the rear speaker in the passenger area; if you want to improve the sound field signal-to-noise ratio, you should refer to the speaker incident pressure amplitude setting plan of Plan 3, increase the incident pressure amplitude of the front and middle speakers in the passenger area, and lower the incident pressure amplitude of the rear speaker in the passenger area. Plan 6 is the most uniform solution for the overall sound field in the car. The sound field unevenness of each frequency under this plan is compared with the preliminary plan. Except for a slight increase in the sound field unevenness at 250Hz, the other frequencies are significantly reduced, and the largest decrease is at 500Hz, reaching 3.98dB; the signal-to-noise ratio of the sound field in the car of Plan 3 is improved by 1.5dB compared with the preliminary plan.

[0130] When analyzing the influence of the selection and layout of interior materials on the unevenness of the sound field in the bus through simulation in COMSOL, it was found that the change of interior materials did not significantly change the unevenness of the sound field in the bus. Therefore, this embodiment only analyzes the influence of the selection and layout of interior materials on the signal-to-noise ratio. Since the material area used for the instrument panel is small, the use of different materials has little effect on the signal-to-noise ratio of the overall sound field. Therefore, the material selection of the instrument panel can be ignored, and plastic and polyurethane foam filling are selected according to the preliminary selection plan; Fig.37 As shown in the figure, by changing the material selection and layout of each interior decoration, the signal-to-noise ratio of the car sound field in a total of ninety situations is simulated. It can be seen from the figure that the highest signal-to-noise ratio is scheme 21, which is 25.9dB. The corresponding selection and layout of interior decoration materials are: ordinary PVC plastic is used for bus seats, plywood and artificial leather are used for the inner surface and side panels of the ceiling, ordinary PVC plastic is used for the floor, and ABS engineering plastic is used for the door.

[0131] From the analysis, it can be seen that the preferred solutions for the two indicators of sound field unevenness and signal-to-noise ratio in terms of speaker layout and number are the same, that is, 5 speakers are symmetrically and evenly arranged. Moreover, since the change of interior materials has almost no effect on the unevenness of the sound field in the car, the two indicators differ only in the setting scheme of the speaker incident pressure amplitude. Based on the preliminary speaker layout scheme, this embodiment changes the number of speakers and considers a symmetrical and even arrangement scheme. In addition, considering that in the interior of the bus, compared with the sound field balance, passengers usually expect to hear the audio content clearly. After comparing the simulation results of various schemes, finally, as shown in FIG. Fig.38As shown in the figure, it is the most suitable solution. There are six speakers in total, which are symmetrically distributed on the left and right. The front and rear intervals are 4.5 meters. The pressure amplitude of the speakers in the driving area is 0.5Pa, the pressure amplitude of the speakers in the front and middle of the passenger area is 0.45Pa, and the pressure amplitude of the speakers in the rear of the passenger area is 0.55Pa. The selection and layout of interior materials are as follows: ordinary PVC plastic is used for bus seats, plywood is used for the inner surface of the ceiling and the side panels, and artificial leather is laid on the surface. Ordinary PVC plastic is used for the floor, and ABS engineering plastic is used for the door. The COMSOL simulation results of the sound pressure level of each measuring point after comprehensive consideration of the influencing factors of the speakers in the car are as follows Fig.39 As shown, Fig.40 As shown in the figure, the comparison value of the signal-to-noise ratio of the car sound field and the initial solution is 11.64dB higher than the initial solution. It can be seen that the optimization result is better and the signal quality of the loudspeaker broadcast sound propagation is guaranteed; Fig.41 As shown in the figure, it is the sound field unevenness at each frequency after comprehensive optimization. It can be seen from the figure that the overall unevenness of the bus has been significantly reduced after comprehensive optimization. The most obvious decrease in sound field unevenness after optimization compared with the preliminary solution is 16.95dB at 2000Hz. The unevenness reduction values ​​at 250Hz and 1000Hz are also greater than 10dB, and the unevenness values ​​at 500Hz and 4000Hz are both greater than 5dB. After comprehensively considering the number and layout of speakers, the optimization can significantly improve the uniformity of the sound field in the bus. In order to more intuitively understand the sound field unevenness in the listening area, as shown in the figure, Figure 42-49 As shown, this embodiment selects four planes corresponding to the front seat height, front standing height, rear seat height and rear standing height of the bus, and analyzes and compares the sound pressure levels of the four planes in front and behind the bus for comprehensive optimization. It can be seen from the figure that after comprehensive optimization, the sound field unevenness of the main listening planes in the bus is significantly reduced.

[0132] The invention designs and develops an optimization method for the interior sound field design of a bus. The method takes a city bus as a research object, uses COMSOL Multiphysics software to complete the simulation of the interior sound field of the bus, and takes the optimization simulation of acoustic performance as the main goal from the perspectives of the selection and arrangement of the speakers in the bus, the selection and laying method of the interior decoration materials, etc., and performs acoustic comprehensive optimization design on the sound field related factors such as the interior sound system and the interior decoration arrangement, thereby providing relevant suggestions for the production and manufacturing of the bus, improving the balance and consistency of the sound at different positions, helping to improve the clarity of speech and reduce interference, and being able to improve production efficiency and reduce production costs.

[0133] Although the embodiments of the present invention have been disclosed as above, they are not limited to the applications listed in the specification and the implementation modes. They can be fully applied to various fields suitable for the present invention. For those familiar with the art, additional modifications can be easily implemented. Therefore, without departing from the general concept defined by the claims and the scope of equivalents, the present invention is not limited to the specific details and the embodiments shown and described herein.

Claims

1. A method for optimizing a bus interior sound field design, characterized in that: The steps include: Step 1: Collect real vehicle size data and build a city bus model; Step 2: setting initial values ​​of speaker optimization parameters and initial values ​​of interior material optimization parameters in the city bus model, and measuring the vehicle sound field non-uniformity and vehicle signal-to-noise ratio at different frequencies at multiple measurement points; Step 3: adjusting the speaker optimization parameters and the interior material optimization parameters according to the sound field non-uniformity of the whole vehicle and the signal-to-noise ratio of the whole vehicle to obtain the optimal speaker optimization parameters and the interior material optimization parameters; Among them, when the sound field unevenness of the whole vehicle is the smallest and the signal-to-noise ratio of the whole vehicle is the highest, the speaker optimization parameters and interior material optimization parameters are optimal.

2. The method for optimizing the interior sound field design of a bus according to claim 1, characterized in that: In the step 1, a city bus model is constructed by using COMSOL Multiphysics.

3. The method for optimizing the interior sound field design of a bus as claimed in claim 2, characterized in that: The optimized parameters of the speaker include: The incident pressure field amplitude of the loudspeaker sound source, the arrangement of the loudspeakers and the number of loudspeakers.

4. The method for optimizing the interior sound field design of a bus as claimed in claim 3, characterized in that: The interior material optimization parameters include: The material of interior materials, the properties of interior materials and the laying method of interior materials.

5. The method for optimizing the interior sound field design of a bus as claimed in claim 4, characterized in that: The multiple measuring points are respectively arranged at the right ear of a driver in a sitting position, the right ears of passengers in different passenger areas in a sitting position, and the right ears of passengers in different passenger areas in a standing position, and the number of the measuring points is 11.

6. The method for optimizing the interior sound field design of a bus as claimed in claim 5, characterized in that: The step 2 also includes: The city bus model is divided into grids, and each grid accommodates at least six sound wave wavelengths.

7. The method for optimizing the interior sound field design of a bus as claimed in claim 6, characterized in that: The different frequencies include 125 Hz, 250 Hz, 500 Hz, 1000 Hz, 2000 Hz and 4000 Hz.

8. The method for optimizing the interior sound field design of a bus as claimed in claim 7, characterized in that: The calculation formula of the vehicle sound field unevenness is: ΔP max =P max -P min ; Where ΔP max is the sound field unevenness, P max is the maximum sound pressure level simulation value in the listening area of ​​the car, P min It is the minimum sound pressure level simulation value in the listening area of ​​the car.

9. The method for optimizing the interior sound field design of a bus as claimed in claim 8, characterized in that: The calculation formula of the vehicle signal-to-noise ratio is: Δ=Lp y -Lp n ; Where SNR is the signal-to-noise ratio, p s is the sound pressure of signal s, p n is the sound pressure of the background noise n, Δ is the difference between the sound pressure level of the noisy signal and the sound pressure level of the background noise, Lp y is the sound pressure level of the noisy signal y, Lp n is the sound pressure level of background noise n.

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