Rapid method for evaluating noise reduction performance of acoustic package material of electric drive assembly

Abstract

The invention discloses a rapid method for evaluating the noise reduction performance of an acoustic package material of an electric drive assembly. The method comprises the following steps: S1, building a test model; a three-dimensional model composed of the maximum length, width and height of the to-be-tested electric drive assembly is shrunk, and a metal shell with an adjustable sound source in an inner cavity is manufactured. Determining a noise source according to the noise level of the original electric drive assembly order; and S2, sound packet sample preparation and installation. According to the design of the acoustic bag, the average thickness of the acoustic bag coating surfaces is evaluated, and six acoustic bag coating surfaces are manufactured. And according to the designed coating rate, holes are formed in the six coating surfaces, so that the requirement of the designed coating rate is met. And S3, testing, evaluating and verifying. A microphone is arranged at a certain distance from the outside of a metal shell, a noise source in the shell is started, radiation noise of a silent acoustic packet is obtained, then the surface of the shell is coated with an acoustic packet material, the surface radiation noise of the acoustic packet material is measured, and the noise reduction performance of the acoustic material or the acoustic packet considering the perforated structure can be rapidly evaluated.

Description

Technical Field

[0001] The invention belongs to the technical field of automobile acoustic package material development, and in particular relates to a quick method for evaluating the noise reduction performance of an electric drive assembly acoustic package material. Background Art

[0002] In recent years, the number of new energy vehicles in the Chinese market has continued to increase. At the same time, in order to meet consumers' increasing demand for performance, a series of high-power electric drive systems have emerged, which is the current trend of electric vehicle development. The biggest side effect of high-power electric drive assembly systems is noise radiation. Different from the noise generation principle of internal combustion engines, the noise order of electric drives is more diverse, the components are more complex, and the sound quality of electric drives is poor. Unlike engines, most customers cannot accept it. When the structure of the electric drive body cannot be further optimized and the noise level still does not meet the requirements, wrapping the electric drive assembly with an acoustic package has become one of the noise reduction treatment methods for electric drive assemblies by mainstream manufacturers.

[0003] In general, to verify the noise reduction performance of the acoustic package material, it is necessary to conduct the test in a professional anechoic chamber-reverberation chamber, place the sample on the soundproof "window", and test the insertion loss of the material. When verifying the noise reduction effect of the acoustic package parts, it is necessary to test on the electric drive bench, mainly testing the noise level before and after the installation of the acoustic package to evaluate the acoustic effect. Regardless of the above test scheme, the testing cost is high and the test cycle is long, especially for bench tests. Generally, suppliers of acoustic packages rarely have the corresponding resources to conduct bench tests for different projects, and host manufacturers, due to various factors, cannot meet the repeated verification of different acoustic package products provided by suppliers.

[0004] The accumulation of data on the acoustic properties of materials is the basis for the development of acoustic packages. A quick and effective way to obtain the acoustic properties of materials is to test the acoustic impedance tube in the laboratory, but this method is only more effective for the early development of materials and is not accurate enough for the actual acoustic performance. In general, the use of impedance tubes to test the sound insulation is limited by the size of the material, and there will be large errors at low frequencies. In addition, the sound insulation test is not the same as the insertion loss test method, and it cannot be directly judged based on the sound insulation results. In addition, the acoustic package parts are installed on the electric drive assembly, and various mounting holes or wiring harnesses must be avoided. Holes need to be opened on the product surface during design, which will further affect the acoustic characteristics of the product. These are all issues that need to be considered during product development.

[0005] Therefore, before product design, the acoustic performance of different materials and after openings can be quickly and effectively evaluated, which can not only give an effective judgment on the overall acoustic performance, but also accumulate more accurate material acoustic performance data, while saving the cost of acoustic package bench testing. This is of great significance both for product data accumulation and quick response to noise reduction performance in electric drive development. Summary of the invention

[0006] In order to solve the defects of the prior art, the present invention provides a quick method for evaluating the noise reduction performance of the acoustic package material of the electric drive assembly.

[0007] In order to solve the above technical problems, the present invention provides the following technical solutions:

[0008] The present invention provides a quick method for evaluating the noise reduction performance of an acoustic package material of an electric drive assembly, comprising the following steps:

[0009] S1, test model construction;

[0010] A three-dimensional model is constructed with the maximum length, width, and height of the electric drive assembly to be evaluated, and the model is reduced in size at a ratio of 1:k to form a metal shell. According to the key order noise level of the original electric drive assembly, a suitable sound source is determined, and the sound source is placed in the metal shell to ensure that the radiated noise is close to the order noise of the original electric drive assembly.

[0011] S2, sound package sample preparation and installation;

[0012] According to the product design requirements, the average thickness of the acoustic package covering surface is evaluated, and six covering surfaces of the acoustic package are manufactured according to the surface size of the metal shell. According to the designed coverage rate, holes are opened on the six covering surfaces so that the coverage rate after the holes are opened is the designed coverage rate;

[0013] S3, test evaluation and verification;

[0014] A microphone is set at a set distance from the outside of the metal shell. At this time, there is no acoustic package on the surface of the metal shell. The sound source inside the metal shell is turned on to obtain the radiation noise F(f) of the metal shell when the sound source passes through the acoustic package. oct ); Wrap the acoustic bag with openings on the surface of the metal shell, open the sound source inside the metal shell again, and obtain the radiated noise F" (f oct ); The difference between the radiated noise of the sound source passing through the metal shell without acoustic package and the radiated noise of the sound source passing through the metal shell with acoustic package with openings is the noise reduction performance of the corresponding acoustic package in each frequency band, which can effectively evaluate the performance of the acoustic package.

[0015] Preferably, the method for determining a suitable sound source in step S1 is as follows: obtaining the key order noise curve of the original electric drive assembly, and testing and obtaining the radiation noise of the six frequencies of the electric drive assembly without an acoustic package at the speed corresponding to each order according to the relationship between the motor speed and the order. The noise spectrum is the radiation noise F(f oct ), determine the sound spectrum S(f) of the sound source in the metal shell through the transmission loss of the metal shell;

[0016] S(f)=F(foct )+Tl(f)

[0017] Tl(f)=20*lg(f*M)-47.5

[0018] Wherein, Tl(f) is the sound insulation of the metal shell, f is the frequency, and M is the surface density of the metal shell.

[0019] Preferably, in step S1 and step S2, the electric drive assembly to be evaluated is regarded as a rectangular parallelepiped under three-dimensional coordinates, and the maximum length, width and height dimensions under the three-dimensional coordinates are obtained, and the reduction ratio k value range is 1.5-3; when the acoustic package is coated on the surface of the metal shell, the coating surfaces are bonded by adhesive tape buckles, and one end of the adhesive tape buckle is fixed to the acoustic package by a code pin to facilitate the installation and removal of each coating surface.

[0020] Preferably, the average thickness of the acoustic package in step S2 is determined as follows: the minimum thickness value and the maximum thickness value of the acoustic package in the coating area of ​​each coating surface of the acoustic package are obtained, and the thickness is divided into several thickness intervals, and the actual coating area of ​​each thickness interval is determined. The average thickness of the acoustic package is obtained by the following formula:

[0021]

[0022] Among them, d i-1 is the minimum thickness value for each thickness interval, d i is the maximum thickness value of each thickness interval, s i is the actual package area of ​​each thickness interval, and r is the number of equally divided thickness intervals.

[0023] Preferably, the method of opening holes on the covering surface of the acoustic package in step S2 is as follows: the opening area of ​​each surface is calculated according to the coverage of the acoustic package design and the area of ​​each surface of the metal shell; the surface of the acoustic package material is cut with a unit circle cutter with a radius of 1 to simulate the actual opening state of the electric drive assembly, and the number of opening rows and opening columns of each surface is determined by the following formula:

[0024]

[0025] Among them, p is the number of rows of openings, q is the number of columns of openings, m is the long side dimension of each surface, n is the short side dimension of each surface, and S is the coverage of the acoustic package design.

[0026] Preferably, the measurement point arrangement method during the test in step S3 is to fix the sound source inside the metal shell, close the metal shell, and place the metal shell in the air by suspending through four endpoints of the upper surface, and ensure that the distance between at least five surfaces and the nearest obstacle is not less than 1 meter; at the same time, a microphone is arranged at a distance of 1 / k meters from each surface, k is a reduction ratio, and the k value range of the reduction ratio is 1.5-3.

[0027] Preferably, the radiated noise of the sound source passing through the metal shell without acoustic package and the radiated noise of the sound source passing through the metal shell with acoustic package with openings in step S1 and step S3 are both obtained in the following manner: using a microphone to measure the radiated noise of each surface when the sound source makes a sound, and recording it as time domain data, converting it into a narrowband spectrum using a Fourier transform algorithm, and further converting it into a 1 / 3 octave spectrum; then, subtracting the sound pressure levels at each frequency of the 1 / 3 octave before and after the installation of the acoustic package, that is, obtaining the attenuation effect of the material on the noise radiation, based on which the effect of the actual acoustic package after being installed in the electric drive assembly can be predicted and optimized.

[0028] Compared with the prior art, the present invention has the following beneficial effects:

[0029] The present invention is based on a bench test method for an electric drive assembly and a window insertion loss test method for a material reverberation-anechoic chamber, and is optimized on this basis, thereby overcoming the high cost problem caused by actual bench testing. It can quickly and effectively respond to the acoustic performance evaluation needs of electric drive assemblies for acoustic packages of different materials, while also saving the initial development costs of acoustic package manufacturers. It can also accumulate acoustic data of different materials and effectively guide product development in combination with the cost of materials, thereby providing a better solution for the development of electric drive NVH performance and the application of acoustic materials, especially the development and application of porous materials such as polyurethane. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 A flowchart of a quick method for evaluating the noise reduction performance of an acoustic package material of an electric drive assembly according to the present invention;

[0031] Figure 2 These are the evaluation results of the acoustic package without holes and the acoustic package with holes in the application examples of the present invention. DETAILED DESCRIPTION

[0032] The following detailed description of exemplary embodiments of the present invention refers to the accompanying drawings, which form a part of the description, and in which exemplary embodiments of the present invention that can be implemented are shown as examples. Although these exemplary embodiments are described in sufficient detail to enable those skilled in the art to implement the present invention, it should be understood that other embodiments can be implemented and various changes can be made to the present invention without departing from the spirit and scope of the present invention. The following more detailed description of the embodiments of the present invention is not intended to limit the scope of the claimed invention, but is only for the purpose of illustrating and not limiting the description of the characteristics and features of the present invention, so as to propose the best mode for performing the present invention and to enable those skilled in the art to implement the present invention. Therefore, the scope of the present invention is limited only by the appended claims.

[0033] From the perspective of vibration and noise, an obvious difference between the electric drive assembly of new energy vehicles and the engine of fuel vehicles is that the frequency components of the noise are quite different. Compared with fuel engines, the frequency band of electric drive radiation noise is wider and has more order components, such as electromagnetic noise, gear noise, controller noise, etc., which leads to poor sound quality and lacks the unique "sound wave" surging feeling when fuel vehicles accelerate. These characteristics of motor noise are contrary to the "comfortable driving experience" pursued by the performance development of new energy vehicles. Therefore, reducing the noise of the electric drive assembly is one of the key indicators to improve the NVH performance of the whole vehicle.

[0034] Installing an acoustic package on the motor housing is an effective way to deal with the radiated noise of the electric drive assembly. The acoustic performance of the material is obtained through professional reverberation-anechoic chamber testing, which can assist in predicting the acoustic performance of the acoustic package. However, due to the complex surface structure and many curved surfaces of the electric drive, many parts and wiring harness avoidance issues are involved during installation, which requires different structures, different material thicknesses, and openings on the surface of the acoustic package. Therefore, the electric drive assembly bench test is used to evaluate the NVH performance of the acoustic package.

[0035] When the acoustic package is coated on the surface of the electric drive, it not only needs to block the air noise transmitted by the electric drive assembly, but also reduce the vibration and structural noise on the shell surface. Therefore, the performance of the acoustic package needs to be evaluated not only from the perspective of material performance, but also by changing various material parameters. At the same time, the performance attenuation under the actual structure and surface opening state is also an important factor that needs to be considered in the development of acoustic package products.

[0036] like Figure 1 As shown, this embodiment provides a quick method for evaluating the noise reduction performance of the acoustic package material of the electric drive assembly, comprising the following steps:

[0037] S1. Test model construction.

[0038] Consider the electric drive assembly as a cuboid in three-dimensional coordinates, and obtain the maximum length, width, and height values ​​in three coordinates, which are l, m, and n respectively. According to the maximum size, make the corresponding rectangular metal shell, and the three-coordinate dimensions of the metal shell are Where k is the reduction ratio, the k value range is 1.5-3, the metal shell is made of aluminum, and the thickness is set to 2mm. During the test, the sound source is fixed and enclosed inside the shell to simulate the actual motor sound source.

[0039] S2. Preparation and installation of acoustic package.

[0040] According to product design requirements, the average thickness of the acoustic package is evaluated, and six covering surfaces of the acoustic package are made according to the surface size of the metal shell. According to the designed coverage, holes are opened on the six covering surfaces so that the coverage after opening the holes is the designed coverage.

[0041] According to the product design requirements, determine the average thickness of the model acoustic package. Output the maximum thickness value d of the acoustic package from the design drawing r and the minimum thickness value d0, and is equally divided into r thickness intervals, namely [d0, d1], [d1, d2], ..., [d r-2 , d r-1 ],[d r-1 , d r ], the coverage area of ​​each thickness interval is s1, s2, s3...s r , then the average thickness of the acoustic package of the sample is for:

[0042]

[0043] Among them, d i-1 is the minimum thickness value for each thickness interval, d i is the maximum thickness value of each thickness interval, s i is the actual package area of ​​each thickness interval, and r is the number of equally divided thickness intervals.

[0044] According to the average thickness, the thickness of the sound insulation layer and the sound absorption layer is determined. At the same time, according to the size of the metal shell, the six covering surfaces of the acoustic package are made. The covering surfaces are bonded together by adhesive tape buckles, and one end of the adhesive tape buckle is fixed to the acoustic material by a staple to facilitate the installation and removal of each covering surface.

[0045] Define the design coverage S of the electric drive assembly acoustic package, and the areas of the six covering surfaces of the metal shell are a1, a2...a6, respectively, and the opening area of ​​each covering surface is (1-S)a1, (1-S)a2...(1-S)a6. The way to make holes in the acoustic package is to cut the surface of the material with a unit circle cutter with a radius of 1 to simulate the installation holes or wiring harness avoidance holes involved in the actual state of the electric drive assembly. Therefore, for the metal shell covering surface with an area of ​​a1, the number of holes required is (1-S)a1 / π. Define the long side of the rectangle with a surface area of ​​a1 as m and the short side as n. The openings on the surface are arranged in p rows and q columns, then:

[0046]

[0047] The opening methods of other surfaces are similarly deduced to obtain the actual covering state of the simulated acoustic package.

[0048] S3. Acoustic test evaluation and verification.

[0049] After the sound source is adjusted, it is placed inside the aluminum shell. When the sound source makes a sound, it simulates the state of the electromagnetic noise and gear noise inside the electric drive assembly propagating into the air through the shell surface. It is regarded as a point sound source, radiating sound energy to the surroundings. To ensure that there is no reflection in the near field when the sound source makes a sound, the aluminum shell is suspended in the air through the four endpoints of the upper surface, and at least five surfaces are at least 1 meter away from the nearest obstacle. At the same time, at the distance from each surface The microphone is arranged at meters, and k is the reduction ratio.

[0050] When the sound source is stable, the microphone measures the radiated noise of each surface of the metal shell without acoustic package for no less than 15 seconds, and records the time domain data F(t) in WAV audio format. The Fourier transform algorithm of digital signal analysis software is used to convert the time domain data into a narrowband spectrum F(f), and further, it is converted into an octave spectrum F(f) through integration of a specific frequency band. oct ).

[0051] Using the same method, when the outer surface of the metal shell is covered with an acoustic package, the radiation noise F" (f oct ), then the acoustic performance of the sound package is I' m as follows:

[0052] I' m =F(f oct )-F″(f oct ).

[0053] like Figure 2As shown in the figure, as an application example, a new energy electric drive assembly has obvious radiated noise at the 11.73th order under positive torque, and the sound quality is poor, so an acoustic package needs to be installed to absorb or isolate the propagation of noise. In order to evaluate the attenuation effect of the acoustic package on sound energy, the sound insulation layer material of the acoustic package is ethylene-vinyl acetate copolymer (EVA), and the soft layer sound absorption or damping material is a polyurethane (PU) porous foam material generated by chemical reaction of polyether polyol and isocyanate. The composite structure of the two and the acoustic attenuation effect in the open-cell state are used as evaluation indicators to illustrate the implementation case of the quick evaluation method for the change of NVH performance after the electric drive assembly is equipped with an acoustic package.

[0054] The maximum dimensions obtained from the three-dimensional coordinates of the electric drive assembly are 50cm, 40cm, and 40cm, respectively. If the reduction ratio is set to 1:2, the corresponding metal aluminum cavity dimensions are 25cm, 20cm, and 20cm, respectively.

[0055] The order noise of the electric drive is extracted from the bench test. The speed range is 2000-10000r / min. The frequency corresponding to 11.73 is 390-1955Hz, the corresponding 1 / 3 octave range is about 400-2000Hz, and the noise range is 55-75dB(A). The narrowband spectrum is converted into a 1 / 3 octave spectrum to obtain the sound pressure level value in each 1 / 3 octave. The spectrum is the sound collected by the fixed microphone after the sound source passes through the aluminum shell. According to step S1, the radiated noise F(f oct ).

[0056] The sound insulation value Tl(f) of the aluminum shell in the 1 / 3 octave band of the above frequency band is calculated according to the sound insulation formula of the single-layer material, that is:

[0057] Tl(f)=20*lg(f*M)-47.5

[0058] Where f is the frequency, M is the surface density of the aluminum shell, in kg / m 2 .

[0059] Therefore, the sound source noise spectrum S(f) that needs to be adjusted is

[0060] S(f)=F(f oct )+Tl(f).

[0061] This spectrum is the theoretical value of the sound source. To ensure the effective sound generation of the sound source and accurately identify the sound insulation performance of the wrapping material, the difference between the actual sound source and the theoretical value should be kept within a positive tolerance of 0-5dB. That is, if the radiation noise of the shell is 60dB and the theoretical sound source radiation noise is 67dB, the actual debugging of the sound source should be kept at 67-72dB.

[0062] In this embodiment, the sound insulation material of the acoustic bag is EVA, with a gram weight of 4kg / m 2 Material, thickness is 2mm, polyurethane foam density is 80kg / m 3 Materials. According to the design scheme, the thickness range of the electric drive acoustic package is 0-33mm. According to the calculation method in step S2, the average thickness of the package is 21mm. Considering that the thickness of the EVA material is 2mm, the thickness of the acoustic package is 19mm. According to this thickness and the above-mentioned package size, six surface material package surfaces are made. Each package surface is bonded by a Velcro buckle, and one end of the Velcro buckle is fixed to the acoustic material by a staple to facilitate the installation and removal of each package surface.

[0063] The design coverage of this acoustic package is about 70%. Taking the upper surface area of ​​the aluminum shell of 25cm*20cm as an example, according to the hole-making method of step S2, holes are made on the surface with a cutter per unit area, and the number of rows p is 8 and the number of columns q is 6. The same is true for other covering surfaces, and the state of the acoustic package simulating the actual covering is obtained.

[0064] During the test, the sound source is fixed in the aluminum shell, the gaps in the shell are sealed, and it is suspended in the air with lightweight ropes at four points on the upper surface of the aluminum shell. The five surfaces except the upper surface are kept at least 1 meter away from the nearest obstacle, and a sound collector with recording function is arranged 0.5m from the surface of the aluminum shell.

[0065] An acoustic package without openings is installed on the surface of the aluminum shell, that is, only the attenuation of the sound radiation energy by the material is considered. The sound source is controlled to sound. After the sound source is stable, the recording time of the sound collector is set to 15 seconds and saved as audio data in WAV format. The data is a sound pressure level curve with time as the independent variable. According to step S3, the Fourier transform function of the noise signal processing software is used to convert the time signal F(t) into a 1 / 3 octave spectrum F'(f oct In the same way, an acoustic package with openings with a coverage rate of 70% was installed on the shell surface, and the final measured transmission sound pressure spectrum was F = "(f oct ). Then we can get 4kg / m 2 The attenuation effect of the EVA+21mmPU thick non-perforated material composite state on the noise radiation of the electric drive assembly m And the noise attenuation I' of the actual open hole structure state m :

[0066] I m =F(f oct )-F'(f oct );

[0067] I' m =F(f oct )-F”(foct ).

[0068] According to the above method, the 11.73-order noise problem of the electric drive assembly can be calculated, and the test results under the EVA+PU full coverage and 70% coverage shell models can be obtained, as shown in the figure. Figure 2 The acoustic package full coverage curve I is shown m And 70% coverage curve I' m comparison.

[0069] From the comparison results of this embodiment, it can be seen that the composite structure composed of a sound-insulating heavy layer of EVA + porous foamed sound-absorbing material PU will have a better effect on noise attenuation. In theory, the higher the frequency, the better the noise reduction effect. However, from the test verification of many benches, it can be seen that the actual noise reduction effect is not ideal. It can be seen from this evaluation method that due to the structural influence of the acoustic package, the high-frequency band that should theoretically have good sound attenuation, such as the frequency band above 1000Hz in this solution, has a greatly reduced actual attenuation amplitude, while the low-frequency band that originally has relatively limited noise reduction ability, such as the frequency band below 1000Hz in this solution, has little effect on its sound attenuation due to the open-pore structure of the package material. It further illustrates the importance of qualitative and quantitative pre-evaluation of the noise attenuation of the electric drive assembly by different materials, and prevents the direct bench testing of the materials from failing to achieve the desired effect, resulting in a huge waste of testing resources.

[0070] In this embodiment, only one material solution is used as an example. For the same electric drive and the same noise problem, other materials can be directly replaced for testing in the future without debugging the sound source. This improves the efficiency of material selection and can form effective data accumulation for material suppliers.

[0071] Finally, it should be noted that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art can still modify the technical solutions described in the aforementioned embodiments or replace some of the technical features therein by equivalents. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A quick method for evaluating the noise reduction performance of electric drive assembly acoustic package materials, characterized in that: The following steps are involved: S1, test model construction; A three-dimensional model is constructed with the maximum length, width, and height of the electric drive assembly to be evaluated, and the model is reduced in size at a ratio of 1:k to form a metal shell. According to the key order noise level of the original electric drive assembly, a suitable sound source is determined, and the sound source is placed in the metal shell to ensure that the radiated noise is close to the order noise of the original electric drive assembly. S2, sound package sample preparation and installation; According to the product design requirements, the average thickness of the acoustic package covering surface is evaluated, and six covering surfaces of the acoustic package are manufactured according to the surface size of the metal shell. According to the designed coverage rate, holes are opened on the six covering surfaces so that the coverage rate after the holes are opened is the designed coverage rate; S3, test evaluation and verification; A microphone is set at a set distance from the outside of the metal shell. At this time, there is no acoustic package on the surface of the metal shell. The sound source inside the metal shell is turned on to obtain the radiation noise F(f) of the metal shell when the sound source passes through the acoustic package. oct ); Wrap the acoustic bag with openings on the surface of the metal shell, open the sound source inside the metal shell again, and obtain the radiated noise F" (f oct ); The difference between the radiated noise of the sound source passing through the metal shell without acoustic package and the radiated noise of the sound source passing through the metal shell with acoustic package with openings is the noise reduction performance of the corresponding acoustic package in each frequency band, which can effectively evaluate the performance of the acoustic package.

2. The quick method for evaluating the noise reduction performance of the acoustic package material of the electric drive assembly according to claim 1, characterized in that: The method for determining a suitable sound source in step S1 is as follows: obtaining the key order noise curve of the original electric drive assembly, and testing and obtaining the radiation noise of the six surfaces of the electric drive assembly without an acoustic package at the speed corresponding to each order according to the relationship between the motor speed and the order. The noise spectrum is the radiation noise F(f oct ), determine the sound spectrum S(f) of the sound source in the metal shell through the transmission loss of the metal shell; S(f)=F(f oct )+Tl(f) Tl(f)=20*lg(f*M)-47.5 Wherein, Tl(f) is the sound insulation of the metal shell, f is the frequency, and M is the surface density of the metal shell.

3. The quick method for evaluating the noise reduction performance of the acoustic package material of the electric drive assembly according to claim 1, characterized in that: In the steps S1 and S2, the electric drive assembly to be evaluated is regarded as a cuboid in three-dimensional coordinates, and the maximum length, width, and height dimensions in the three-dimensional coordinates are obtained, and the reduction ratio k value range is 1.5-3; when the acoustic package is coated on the surface of the metal shell, the coated surfaces are bonded by adhesive tape buckles, and one end of the adhesive tape buckle is fixed to the acoustic package by a code pin to facilitate the installation and removal of each coated surface.

4. The quick method for evaluating the noise reduction performance of the acoustic package material of the electric drive assembly according to claim 1, characterized in that: The average thickness of the acoustic package in step S2 is determined as follows: the minimum thickness value and the maximum thickness value of the acoustic package in the covering area of ​​each covering surface of the acoustic package are obtained, and the thickness value is divided into several thickness intervals, and the actual covering area of ​​each thickness interval is determined. The average thickness of the acoustic package is obtained by the following formula: Among them, d i-1 is the minimum thickness value for each thickness interval, d i is the maximum thickness value of each thickness interval, s i is the actual package area of ​​each thickness interval, and r is the number of equally divided thickness intervals.

5. The quick method for evaluating the noise reduction performance of the acoustic package material of the electric drive assembly according to claim 1, characterized in that: The method of opening holes on the covering surface of the acoustic package in step S2 is as follows: the opening area of ​​each surface is calculated according to the coverage rate of the acoustic package design and the area of ​​each surface of the metal shell; the surface of the acoustic package material is cut with a unit circle cutter with a radius of 1 to simulate the actual opening state of the electric drive assembly, and the number of opening rows and columns of openings on each surface is determined by the following formula: Among them, p is the number of rows of openings, q is the number of columns of openings, m is the long side dimension of each surface, n is the short side dimension of each surface, and s is the coverage of the acoustic package design.

6. The quick method for evaluating the noise reduction performance of the acoustic package material of the electric drive assembly according to claim 1, characterized in that: The measurement point arrangement method during the test in step S3 is to fix the sound source inside the metal shell, close the metal shell, and place the metal shell in the air through the four endpoints of the upper surface by suspension, and ensure that the distance between at least five surfaces and the nearest obstacle is not less than 1 meter; at the same time, a microphone is arranged at a distance of 1 / k meters from each surface, k is a reduction ratio, and the range of the k value of the reduction ratio is 1.5-3.

7. The quick method for evaluating the noise reduction performance of the acoustic package material of the electric drive assembly according to claim 6, characterized in that: The radiation noise of the sound source passing through the metal shell without acoustic package and the radiation noise of the sound source passing through the metal shell with acoustic package with openings in step S1 and step S3 are both obtained in the following manner: using a microphone to measure the radiation noise of each surface when the sound source makes a sound, and recording it as time domain data, converting it into a narrowband spectrum using a Fourier transform algorithm, and further converting it into a 1 / 3 octave spectrum; then, subtracting the sound pressure levels at each frequency of the 1 / 3 octave before and after the installation of the acoustic package, that is, obtaining the attenuation effect of the material on the noise radiation, based on which the effect of the actual acoustic package after installation in the electric drive assembly can be predicted and optimized.

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