Method for simulating in-vehicle noise during uniform speed driving of a vehicle

Abstract

The application discloses a kind of simulation methods of automobile uniform speed driving in-vehicle noise, including first white noise signal is randomly generated, after being carried out band pass filtering and amplitude calibration respectively, wide frequency noise simulation signal is obtained;Second white noise signal is randomly generated, after being carried out narrowband filtering and narrowband amplitude calibration, narrowband noise simulation signal is obtained;Third white noise signal is randomly generated, band pass filtering signal is generated after filtering, and according to the in-vehicle noise signal sample collected by real vehicle, overall window function is generated, after overall windowing to band pass filtering signal, impact amplitude calibration is generated, and impact noise simulation signal is generated;Wide frequency noise simulation signal, narrowband noise simulation signal, impact noise simulation signal are added to obtain the simulation signal of uniform speed driving in-vehicle noise for playback listening evaluation;The application realizes the simulation of automobile uniform speed driving in-vehicle noise, and the playback effect restores the in-vehicle auditory sensation when real vehicle is uniformly driven, can be quickly adjusted parameter changes sample, carries out playback evaluation to different sample, selects the sample meeting sound quality development requirement, realizes the quick and accurate formulation of uniform speed driving in-vehicle noise development target.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of vehicle noise simulation, in particular to a simulation method for in-vehicle noise of a car running at a constant speed. BACKGROUND

[0002] In-vehicle noise control of a car is an important aspect in the field of car research and development, and the in-vehicle noise index of constant speed running mainly reflects the wind noise and road noise control level of the whole vehicle, and also corresponds to the most perceived use scenario by users. In the past, the total sound pressure level was mainly used to evaluate the in-vehicle noise of constant speed running, but there is a significant problem that sound signals with different frequency spectrum distributions will bring completely different auditory perceptions, even if they have exactly the same total sound pressure level, and the total sound pressure level cannot reflect the influence of narrowband signals and continuous impact signals on auditory perception. Therefore, in practice, the advantages and disadvantages of the total sound pressure level index of some vehicles cannot accurately correspond to the advantages and disadvantages of their actual auditory perception. With the development and improvement of the level of the automotive industry, using the single index of total sound pressure level to evaluate the in-vehicle noise of constant speed running is not enough to support the development and control of high-level sound quality of cars. It is necessary to develop more accurate and detailed in-vehicle noise targets of constant speed running starting from the auditory perception of the human ear, such as the 1 / 3 octave band distribution of in-vehicle noise, the distribution of narrowband noise such as tire cavity noise, and the main frequency range of road impact noise. The above problems need to be solved. SUMMARY

[0003] The purpose of the present application is to provide a simulation method for in-vehicle noise of a car running at a constant speed to solve the problems raised in the background art. The method can finely parameterize the frequency, amplitude, etc. of various components in the signal and quickly generate a large number of signal samples. Car research and development personnel can evaluate the signal samples generated by the method, which can be used to develop in-vehicle noise development targets of constant speed running, or to determine the influence of changes in each component in the signal sample on auditory perception, and then determine the optimization direction.

[0004] To achieve the above purpose, the present application provides the following technical solution: a simulation method for in-vehicle noise of a car running at a constant speed, comprising:

[0005] Collecting in-vehicle noise signal samples of a real car running at a constant speed, determining the frequency range of the simulation signal, dividing the frequency range into a plurality of continuous frequency bands, calculating the average sound pressure of the in-vehicle noise signal samples in each frequency band, the FFT spectrum average result, and the FFT-time time-frequency analysis result;

[0006] Randomly generate a first white noise signal, calculate the ratio of the average sound pressure of the in-vehicle noise signal sample in each frequency band to the average sound pressure of the first white noise signal in each frequency band, and obtain the sound pressure amplitude calibration coefficient of each frequency band; the first white noise signal is respectively band-pass filtered in each frequency band, and then the sound pressure amplitude is calibrated by the corresponding sound pressure amplitude calibration coefficient to obtain a wide-frequency noise simulation signal;

[0007] According to the FFT spectrum average result of the in-vehicle noise signal, the frequency lower limit, the frequency upper limit and the amplitude of a plurality of narrow-band components are determined; the narrow-band amplitude calibration coefficient is set according to the amplitude of each narrow-band component; a second white noise signal is randomly generated, the second white noise signal is filtered according to the frequency lower limit and the frequency upper limit of each narrow-band component, and then the amplitude is calibrated by the narrow-band amplitude calibration coefficient to obtain a narrow-band noise simulation signal;

[0008] According to the FFT-time time-frequency analysis result of the in-vehicle noise signal, the frequency lower limit, the frequency upper limit, the density, the single impact time and the impact amplitude of a plurality of road impact noise components are determined; the impact amplitude calibration coefficient of the corresponding road impact noise component is set according to the impact amplitude;

[0009] A third white noise signal is randomly generated, and a band-pass filtered signal with the same or similar frequency range as the impact noise is generated by band-pass filtering the third white noise signal according to the frequency lower limit and the frequency upper limit of the impact noise component;

[0010] According to the density and single impact time of the impact noise component, a whole window function of the impact noise is generated, and the band-pass filtered signal is whole-windowed by the whole window function, and then the amplitude is calibrated by the impact amplitude calibration coefficient to generate an impact noise simulation signal;

[0011] The wide-frequency noise simulation signal, the narrow-band noise simulation signal and the impact noise simulation signal are added to obtain a simulation signal of in-vehicle noise during uniform speed driving, and the simulation signal is saved in a format that can be played by an electronic device for playback and listening evaluation.

[0012] Further, the in-vehicle noise signal sample of the actual vehicle driving at a uniform speed is collected, the frequency range of the simulation signal is determined, and the frequency range is divided into a plurality of continuous frequency bands, further comprising:

[0013] The frequency range of the simulation signal is determined by the lower limit of the starting frequency band and the upper limit of the ending frequency band, or the frequency range of the simulation signal is determined by actual needs;

[0014] The frequency range of the simulation signal is divided into a plurality of continuous frequency bands using integer or fractional octave frequency bands or fixed bandwidth frequency bands.

[0015] Further, a first white noise signal is randomly generated, a ratio of an average sound pressure of the in-vehicle noise signal sample in each frequency band to an average sound pressure of the first white noise signal in each frequency band is calculated to obtain a sound pressure amplitude calibration coefficient of each frequency band; the first white noise signal is respectively band-pass filtered in each frequency band, and then the sound pressure amplitude calibration coefficient is used for sound pressure amplitude calibration to obtain a wide-band noise simulation signal.

[0016] A one-to-one corresponding wide-band pass filter is set according to a plurality of frequency bands, the first white noise signal is respectively passed through each wide-band pass filter to obtain a plurality of wide-band communication signals, and each wide-band communication signal is amplified and calibrated by the corresponding sound pressure amplitude calibration coefficient to obtain a wide-band noise simulation signal.

[0017] Further, according to the FFT spectrum average result of the in-vehicle noise signal, the frequency lower limit, the frequency upper limit and the amplitude of the plurality of narrow-band components are determined; the narrow-band amplitude calibration coefficient is set according to the amplitude of each narrow-band component; a second white noise signal is randomly generated, the second white noise signal is filtered according to the frequency lower limit and the frequency upper limit of each narrow-band component, and then the narrow-band amplitude calibration coefficient is used for amplitude calibration to obtain a narrow-band noise simulation signal, further comprising:

[0018] The number of the plurality of narrow-band components is determined by the number of main narrow-band components in the FFT spectrum average result of the in-vehicle noise signal and the simulation accuracy requirement;

[0019] The narrow-band band-pass filter is designed according to the frequency lower limit and the frequency upper limit of each narrow-band component;

[0020] The second white noise signal is respectively passed through the corresponding narrow-band band-pass filter to obtain a plurality of narrow-band filter signals of the plurality of narrow-band components;

[0021] The plurality of narrow-band filter signals are respectively amplified and calibrated by the corresponding narrow-band amplitude calibration coefficient to obtain a narrow-band noise simulation signal.

[0022] Further, a third white noise signal is randomly generated, a band-pass filter signal with the same or similar frequency range as the impact noise is generated by band-pass filtering the third white noise signal according to the frequency lower limit and the frequency upper limit of the impact noise component, further comprising:

[0023] A band-pass filter is set according to the frequency lower limit and the frequency upper limit of the impact noise component, and the third white noise is band-pass filtered to generate a band-pass filter signal with the same or similar frequency range as the impact noise.

[0024] Further, the overall window function of the impact noise is generated, the band-pass filter signal is windowed by the overall window function, and then the impact amplitude calibration coefficient is used for amplitude calibration to generate an impact noise simulation signal, further comprising:

[0025] Setting the window function of the impact unit for each impact noise component;

[0026] The time length of the window function of the impact unit is the same as the single impact time;

[0027] Setting the window function value of the start and end time of the window function of the impact unit to zero;

[0028] The window function is twice differentiable in other intervals except the start and end time.

[0029] Further comprising:

[0030] The impact signal is composed of a series of uniformly distributed impact units;

[0031] The number of impacts in the simulation time is obtained by multiplying the impact density by the total time length of the simulation sample;

[0032] According to the number of impacts, a series of uniformly distributed random numbers in the simulation time are generated.

[0033] Further comprising:

[0034] The window function of the impact unit is summed up for the delay time of the number of impacts respectively, to obtain the overall window function, wherein the delay time is the uniformly distributed random number in the simulation time;

[0035] The impact noise simulation signal is generated by multiplying the band-pass filtered signal by the overall window function, then multiplying by the corresponding impact amplitude calibration coefficient.

[0036] Further comprising:

[0037] The band-pass filtered signal is multiplied by the window function of the impact unit to obtain a single impact unit;

[0038] The single impact unit is summed up for the delay time of the number of impacts respectively, to obtain the number of uniformly distributed impact units, wherein the delay time is the uniformly distributed random number in the simulation time;

[0039] The single impact unit is multiplied by the corresponding impact amplitude calibration coefficient, and the impact noise simulation signal is obtained by superposition and summation.

[0040] Further, the wideband noise simulation signal, the narrowband noise simulation signal, and the impact noise simulation signal are added to obtain the simulation signal of the in-vehicle noise of the uniform speed driving vehicle, the simulation signal is saved in a format that can be played by an electronic device for playback and listening evaluation, and further comprising:

[0041] The simulation signal of the synthesized constant-speed driving vehicle interior noise is caused by the addition of the narrow-band noise simulation signal and the impact noise simulation signal, so that the energy of the frequency band where the added signal component is located is increased, the increased energy information of the frequency band is fed back, and each frequency band energy of the synthesized constant-speed driving vehicle interior noise simulation signal is restored to the original sample level;

[0042] The restoration of each frequency band energy of the synthesized constant-speed driving vehicle interior noise simulation signal to the original sample level further comprises:

[0043] The energy of the corresponding frequency band in the wide-band noise simulation signal is reduced by correcting the sound pressure amplitude calibration coefficient, the increased energy information is fed back, and each frequency band energy of the synthesized constant-speed driving vehicle interior noise simulation signal is restored to the original sample level through multiple iterations;

[0044] The sound pressure amplitude calibration coefficient, the narrow-band amplitude calibration coefficient and the impact amplitude calibration coefficient are adjusted to change each component of the simulated synthesized constant-speed driving vehicle interior noise, and different simulation samples are generated.

[0045] The playback and listening evaluation are performed on the various samples generated after adjustment.

[0046] Compared with the prior art, the beneficial effects of the present application are that the signal processing method is used to construct three signal components of wide-band noise, narrow-band noise and road impact noise, the three signal components are superimposed to generate constant-speed driving vehicle interior noise, and the characteristic parameters of the three signal components can be adjusted respectively; the method can realize the simulation of the constant-speed driving vehicle interior noise, the simulated constant-speed driving vehicle interior noise signal sample can be used for playback evaluation, and the playback effect restores the auditory perception in the vehicle during the constant-speed driving of the actual vehicle. The method can quickly adjust the parameters to change the samples, the playback evaluation is performed on different samples, the sample meeting the sound quality development requirements can be quickly selected, the rapid and accurate development goal of the constant-speed driving vehicle interior noise is realized; the influence of different sound components on the auditory perception can be analyzed and judged by comparing the change trend of the auditory perception caused by the change of different parameters, and reliable basis is provided for formulating the optimization scheme of the constant-speed driving vehicle interior noise. BRIEF DESCRIPTION OF DRAWINGS

[0047] Figure 1 The flow chart of the simulation method of the constant-speed driving vehicle interior noise of the automobile in the embodiment of the present application is shown in the figure;

[0048] Figure 2 The 1 / 3 octave result diagram of the constant-speed driving vehicle interior noise of the automobile in the embodiment of the present application is shown in the figure, wherein (a) is not weighted, and (b) is A weighted;

[0049] Figure 3 The 1 / 3 octave result diagram of the first white noise signal in the embodiment of the present application is shown in the figure, wherein (a) is not weighted, and (b) is A weighted;

[0050] Figure 4 The amplitude response schematic diagram of 1 / 3 octave filter in the embodiment of the present application;

[0051] Figure 5 The time domain waveform schematic diagram of 1 / 3 octave band signal in the embodiment of the present application;

[0052] Figure 6 The 1 / 3 octave comparison schematic diagram of wideband noise simulation signal and real vehicle collected signal sample in the embodiment of the present application;

[0053] Figure 7 The FFT spectrum average analysis result schematic diagram of wideband noise simulation sample and original sample in the embodiment of the present application;

[0054] Figure 8 The narrowband filter schematic diagram determined by the main peak value component of original sample in the embodiment of the present application;

[0055] Figure 9 The narrowband component schematic diagram in the narrowband bandpass filtered signal superimposed in the simulation real vehicle noise in the embodiment of the present application;

[0056] Figure 10 The FFT-time time frequency analysis schematic diagram of real vehicle noise signal in the embodiment of the present application;

[0057] Figure 11 The generation schematic diagram of impact unit of impact signal component 1 in the embodiment of the present application, wherein (a) is bandpass filtered signal 1, (b) is time window 1, and (c) is the bandpass filtered signal 1 after windowing;

[0058] Figure 12 The generation schematic diagram of impact unit of impact signal component 2 in the embodiment of the present application, wherein (a) is bandpass filtered signal 2, (b) is time window 2, and (c) is the bandpass filtered signal 2 after windowing;

[0059] Figure 13 The schematic diagram of each impact unit of impact signal component 2 generated according to impact density in the embodiment of the present application;

[0060] Figure 14 The superimposed generated impact signal 2 schematic diagram in the embodiment of the present application;

[0061] Figure 15 The schematic diagram of each impact unit of impact signal component 1 generated according to impact density in the embodiment of the present application;

[0062] Figure 16 The superimposed generated impact signal 1 schematic diagram in the embodiment of the present application;

[0063] Figure 17 Fig. 2 is a schematic diagram of the FFT spectrum average result of the impact signal in an embodiment of the present application;

[0064] Figure 18 Fig. 3 is a schematic diagram of the FFT-time time-frequency analysis result of the impact signal in an embodiment of the present application;

[0065] Figure 19 Fig. 4 is a schematic diagram of the 1 / 3 octave analysis of the synthetic signal Sig combine in an embodiment of the present application, wherein (a) is before amplitude correction, and (b) is after amplitude correction;

[0066] Figure 20 Fig. 5 is a schematic diagram of the 1 / 3 octave analysis of the synthetic signal Sig combine in an embodiment of the present application, wherein (a) is before amplitude correction, and (b) is after amplitude correction;

[0067] Figure 21 Fig. 6 is a schematic diagram of the FFT-time time-frequency analysis verification in an embodiment of the present application, wherein (a) is the noise collected by the real vehicle, and (b) is the synthetic noise signal Sig combine;

[0068] Figure 22 Fig. 7 is a schematic diagram of the FFT spectrum average result of the optimized sample in an embodiment of the present application;

[0069] Figure 23 Fig. 8 is a schematic diagram of the 1 / 3 octave average result of the optimized sample in an embodiment of the present application;

[0070] Figure 24 Fig. 9 is a schematic diagram of the FFT-time time-frequency analysis result comparison of the simulated optimized sample in an embodiment of the present application, wherein (a) is the noise collected by the real vehicle, and (b) is the simulated optimized sample. DETAILED DESCRIPTION

[0071] The technical solutions in the embodiments of the present application will be described clearly and completely below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all the other embodiments obtained by those skilled in the art without creative work fall within the scope of protection of the present application.

[0072] In the description of the present application, unless otherwise specified and limited, the meaning of "a plurality of" is two or more; the orientation or positional relationship indicated by the terms "upper", "lower", "left", "right", "inner", "outer", "front end", "rear end", "head", "tail" and the like is based on the orientation or positional relationship shown in the drawings, and is only for the convenience of describing the present application and simplifying the description, and does not indicate or imply that the device or element referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as a limitation on the present application. In addition, the terms "first", "second", "third" and the like are only for descriptive purposes and cannot be understood as indicating or implying relative importance.

[0073] In the description of the present application, it should be noted that, unless otherwise specified and limited, the terms "connected", "connected" should be understood broadly, for example, it can be fixedly connected, or it can be detachably connected, or integrally connected; it can be mechanically connected, or it can be electrically connected; it can be directly connected, or it can be indirectly connected through an intermediate medium. For those skilled in the art, the specific meaning of the above terms in the present application can be understood according to the specific circumstances.

[0074] Please refer to the drawings, the present application provides a technical solution: as Figure 1 shown, a simulation method of in-vehicle noise of a vehicle driving at a constant speed, comprising the following steps:

[0075] S102, collecting in-vehicle noise signal samples of a real vehicle driving at a constant speed, determining the frequency range of the simulation signal, dividing the frequency range into a plurality of continuous frequency bands, calculating the average sound pressure of the in-vehicle noise signal samples in each frequency band, the FFT spectrum average result, and the FFT-time time-frequency analysis result;

[0076] Specifically, the simulation signal frequency range is determined by the lower limit of the starting frequency band and the upper limit of the ending frequency band, or the simulation signal frequency range is determined by the actual demand; the simulation signal frequency range is divided into a plurality of continuous frequency bands using integer or fractional octave frequency bands or fixed bandwidth frequency bands.

[0077] Preferably, the frequency range of the analog signal in the embodiment is 17.5 Hz to 17959.4 Hz; the frequency range of the analog signal is divided into 30 continuous 1 / 3 octave bands; the selected 1 / 3 octave center frequency is 20 Hz to 16 kHz, and there are 30 1 / 3 octave bands, the analog signal frequency range that can be generated is 17.5 Hz to 17959.4 Hz, covering the normal hearing frequency range of human ear and the main components of the vehicle interior noise; the frequency range division method using other integer or fractional octave bands or fixed bandwidth bands, the analog signal frequency range determined by the lower limit of the starting band and the upper limit of the ending band or determined by the actual demand, and the corresponding number of bands generated in the frequency range by any of the above division methods are also within the protection scope of the application.

[0078] S104, a first white noise signal is randomly generated, the ratio of the average sound pressure of the vehicle interior noise signal sample in each frequency band to the average sound pressure of the first white noise signal in each frequency band is calculated to obtain the sound pressure amplitude calibration coefficient of each frequency band; the first white noise signal is respectively band-pass filtered in each frequency band, and then the wide frequency noise analog signal is obtained by superimposing the sound pressure amplitude calibration after the corresponding sound pressure amplitude calibration coefficient.

[0079] Specifically, a one-to-one corresponding wide band-pass filter is set according to a plurality of frequency bands, the first white noise signal is respectively passed through each band-pass filter to obtain a wide frequency band communication signal, and the wide frequency noise analog signal is obtained by superimposing each wide frequency band communication signal after amplitude calibration by the corresponding sound pressure amplitude calibration coefficient.

[0080] Wherein, the steady-state average sound pressure of the 30 1 / 3 octave bands of the real vehicle uniform speed driving vehicle interior noise signal sample is calculated, denoted as: p_car n , n = 1:30; the steady-state average sound pressure of the 130 1 / 3 octave bands of the first white noise signal is calculated, denoted as p_w n , n = 1:30; the obtained 1 / 3 octave sound pressure of the real vehicle uniform speed driving vehicle interior noise is divided by the 1 / 3 octave sound pressure of the first white noise respectively to obtain the amplitude calibration coefficient, denoted as A_wb n , then the amplitude calibration coefficient calculation formula is: A_wb n = p_car n / p_w n , n = 1:30; the conversion relationship between the amplitude calibration coefficient and the sound pressure level is: L = 20*log 10 (p 2 / p0 2 ) or p = 10 L / 20 *p0, in which: L is the sound pressure level, p is the sound pressure, the reference sound pressure p0 = 2*10 -5Unit: Pa; 30 filters were designed based on a 1 / 3 octave bandpass range: Hd_wb n Where n = 1:30; the first white noise is passed through the above 30 1 / 3 octave bandpass filters to obtain 30 1 / 3 octave bandpass signals Sig_wb. n Its calculation formula is: Sig_wb n =filter(Hd_wb n ,wh itenoise_1),n=1:30; After amplitude calibration of each frequency band signal, they are superimposed to synthesize a broadband noise analog signal, denoted as: Sig_wb_total. The calculation formula for the broadband noise analog signal is:

[0081] For example, such as Figure 2 and Figure 3 As shown, the in-vehicle noise of a real vehicle traveling at a constant speed was collected. Taking the in-vehicle noise of a certain model traveling at a constant speed of 50 km / h on a rough road as an example, 10 seconds of steady-state noise data were collected; its 1 / 3 octave band average result was calculated. Among them, A-weighting is part of the national standard, which can reflect the auditory frequency response characteristics of the human ear and is widely used in environmental noise measurement. The unit is dB(A).

[0082] The calculation results for this example are shown in Table 1:

[0083] Table 1: Center frequency, frequency range, and sound pressure level, sound pressure level, and amplitude calibration coefficient of in-vehicle noise and first white noise during constant speed driving of each 1 / 3 octave band.

[0084]

[0085]

[0086] Design 30 filters Hd_wb based on the 1 / 3 octave bandpass range. n With n = 1:30, this application example uses a 46th-order infinite impulse response elliptic filter for design. The amplitude responses of each 1 / 3 octave band filter are as follows: Figure 4 As shown, the amplitude response of a 1 / 3 octave bandpass filter; 30 1 / 3 octave bandpass signals Sig_wb n Time-domain waveforms such as Figure 5 As shown, for waveform observation, the x-axis range in the figure is only 0.1s in length; the synthesized broadband noise analog signal is compared with the actual vehicle acquired signal sample using A-weighted 1 / 3 octave band comparison, and the results are as follows. Figure 6 As shown, the simulated results of the sound pressure levels in each 1 / 3 octave band are basically consistent with the original samples collected from the actual vehicle.

[0087] The white noise is filtered by 30 1 / 3 octave band pass filters respectively to synthesize a wide frequency noise simulation signal. The frequency distribution characteristics and sound size of the noise can be adjusted by changing the amplitude coefficient of each 1 / 3 octave noise.

[0088] S106, according to the FFT spectrum average result of the in-vehicle noise signal, the frequency lower limit, the frequency upper limit and the amplitude of a plurality of narrowband components are determined; the narrowband amplitude calibration coefficient is set according to the amplitude of each narrowband component; a second white noise signal is randomly generated, the second white noise signal is filtered according to the frequency lower limit and the frequency upper limit of each narrowband component, and the narrowband noise simulation signal is obtained after the amplitude calibration of the narrowband amplitude calibration coefficient is superimposed;

[0089] Specifically, the number of the plurality of narrowband components is determined by the number of main narrowband components in the FFT spectrum average result of the in-vehicle noise signal and the simulation accuracy requirement; the band pass filter is designed according to the frequency lower limit and the frequency upper limit of each narrowband component; the second white noise signal passes through the band pass filter to obtain a plurality of narrowband filter signals of the narrowband components; the narrowband noise simulation signal is obtained after the narrowband filter signals are superimposed after the amplitude calibration of the respective narrowband amplitude calibration coefficient.

[0090] Firstly, the narrowband signal parameters are determined, the FFT spectrum average result of the real vehicle test signal is observed, and the frequency lower limit fl_nb of the main narrowband component is determined. n Secondly, the frequency upper limit fu_nb of the main narrowband component is determined. n Thirdly, the amplitude A_nb of the main narrowband component is determined. n n=1:N, wherein N is determined by the number of main narrowband components in the FFT spectrum average result of the real vehicle noise; secondly, the narrowband filter is set, and the band pass filter Hd_nb is designed according to the frequency lower limit and the frequency upper limit of each peak component. n n=1:N; finally, the narrowband noise simulation signal is generated, the second white noise is randomly generated and is recorded as wh itenoise_2, N narrowband signals are obtained by passing through the above narrowband filter, and the calculation formula is Sig_nb n =filter(Hd_nb n ,wh itenoise_2), wherein n=1:N; the narrowband amplitude calibration coefficient A_nb(n) is set according to the amplitude of each narrowband component in the real vehicle noise sample, is multiplied by Sig_nb(n) respectively, and the superposition result of the narrowband signal is obtained as the narrowband noise simulation signal, and the calculation formula is:

[0091] Understandably, while the broadband noise generated by superimposing 1 / 3 octave bandpass signals may match the original sample in terms of individual 1 / 3 octave band results, it cannot simulate the prominent frequency components in the original sample. Performing FFT spectral averaging analysis on the broadband noise simulation sample in this example and the original sample collected from the actual vehicle reveals several frequency peaks in the original vehicle signal, which the simulation results cannot match. Figure 7 As shown in Table 2, observe and identify the frequency ranges of several major peak components in the original sample.

[0092] Table 2 Main peak components of the original samples

[0093] Figure 8 Figure 8 Figure 9 1 81 92 2 205 210 3 365 400 4 1080 1180 5 1783 1800

[0094] Design a bandpass filter based on the frequency range of each peak component in the table above, such as... Figure 10 As shown, Figure 13 A narrowband filter is determined by the main peak components of the original sample; a second white noise is randomly generated, and five narrowband signals are obtained by passing them through the above narrowband filter. The formula is as follows:

[0095] Sig_nb n =filter(Hd_nb n ,wh itenoise_2), n=1:N

[0096] In this example, the five peaks of the original sample are simulated in a narrowband, so N is set to 5 in this example.

[0097] Based on the amplitude of each narrowband component in the actual vehicle noise sample, A_nb(n) is set, and then multiplied by Sig_nb(n) and summed to obtain the superposition result of the narrowband signals. The formula is as follows:

[0098]

[0099] Narrowband synthesis results as follows Figure 14 As shown, this is the narrowband component in the simulated real vehicle noise superimposed on the narrowband bandpass filtered signal;

[0100] White noise is filtered using a bandpass filter with a freely adjustable bandpass frequency range to synthesize a narrowband noise analog signal. The frequency characteristics of the narrowband noise can be adjusted by changing the upper and lower limits of the bandpass filter and the filter order, and the magnitude of the narrowband noise can be adjusted by changing the amplitude coefficient.

[0101] S108. Based on the FFT-time frequency analysis results of the in-vehicle noise signal, confirm the lower frequency limit, upper frequency limit, density, single impact time, and impact amplitude of multiple road impact noise components; set the corresponding impact amplitude calibration coefficients for the road impact noise components according to the impact amplitude.

[0102] The simulation parameters of the impact signal are determined, and the frequency lower limit fl_pu of the road impact noise component is confirmed by the FFT-time frequency analysis result of the signal collected by the real vehicle n , the frequency upper limit fu_pu n , the density dense_pu n , the impact frequency per unit time, the single impact time pu_time n , and the amplitude A_pu n , wherein n=1:M, and M is determined by the number of road impact noise categories that need to be simulated.

[0103] It can be understood that the FFT-time frequency analysis is performed on the real vehicle noise signal, as shown in Figure 15 , the frequency range, the density (i.e., the impact frequency per unit time), the duration, and the amplitude of the road impact noise component are confirmed. In this example, two impact signals of different intensities are generated to simulate the continuous impact noise and the occasional strong impact noise generated by the real vehicle driving on rough road, and the parameters of the two impact signals are shown in Table 3.

[0104] Table 3 Impact signal simulation parameters

[0105]

[0106] The impact signal is generated according to the impact density, the impact density is multiplied by the total sample duration to obtain the total number of impacts, and the time delay of all impact signals is generated by generating random numbers. In this example, a 10s length sample is to be generated, and according to Table 3, the frequency of impact noise component 2 is 3 times / s, that is, a total of 30 impact units need to be generated. The windowed bandpass filtered signal 2 is copied 30 times, and 30 random numbers uniformly and discretely distributed in 10s are generated as the time delay of each impact unit, to obtain the distribution of all impact units, as shown in Figure 17 and Figure 18 . Similarly, impact noise component 1 will generate 4 impact units in 10s, and 4 random numbers uniformly and discretely distributed in 10s are used to delay the 4 impact units, respectively, to obtain the impact unit distribution of impact noise component 1, as shown in Figure 11 , 16 . The impact signal component 1 and the impact signal component 2 are multiplied by the corresponding amplitude coefficients and added to synthesize the impact signal, and the FFT spectrum average result of the obtained impact signal is shown in Figure 12 . The FFT-time frequency analysis result of the impact signal is shown in Figure 13 . It can be seen that the synthesized impact signal can well simulate the road impact noise component of the real vehicle collected sample in terms of time-frequency characteristics.

[0107] S110, randomly generating a third white noise signal, and performing band-pass filtering on the third white noise signal by using the frequency lower limit and the frequency upper limit of the impact noise component to generate a band-pass filtered signal which is the same as or similar to the impact noise frequency range;

[0108] Specifically, a band-pass filter is set according to the frequency lower limit and the frequency upper limit of the impact noise component, and the third white noise is band-pass filtered to generate a band-pass signal which is the same as the impact noise frequency range.

[0109] wherein the band-pass signal is filtered, the third white noise whitenoise_3 is randomly generated, a band-pass filter Hd_pu is designed by using the frequency lower limit and the frequency upper limit of the impact noise component, and the third white noise is band-pass filtered to generate a band-pass signal which is the same as the impact noise frequency range, and the calculation formula is: n

[0110] Sig_bp n = filter(Hd_pu n , whitenoise_3), where n = 1:M

[0111] It can be understood that the band-pass filter is designed by using the frequency lower limit and the frequency upper limit in Table 3, and the third white noise is band-pass filtered, and the method is the same as the above-mentioned narrow-band signal generation method; then the band-pass signal is truncated by using a time window, and the duration of the window function is determined by the duration in the above table, the amplitudes at the start and end time of the window function should be 0, and should be smoothly rising and falling to avoid signal mutation when the impact signal is synthesized with the previously generated wide-band signal and narrow-band signal, and to avoid the generation of explosive sound; in this example, the time window and the band-pass filtered signal after the window of the two impact signals are shown as Figure 14 and Figure 15

[0112] S112, generating an overall window function of the impact noise according to the density of the impact noise component and the single impact time, and performing overall windowing on the band-pass filtered signal by using the overall window function, and then performing amplitude scaling by using an impact amplitude scaling coefficient to generate an impact noise simulation signal;

[0113] Specifically, an impact unit window function of each impact noise component is set; the time length of the impact unit window function is the same as the single impact time; the window function values at the start and end time of the impact unit window function are set to zero; and the window function is twice differentiable in other intervals except the start and end time.

[0114] wherein the time length of the window function w_unit n of the impact unit is the same as the single impact time pu_time n ​​The window function of the impact unit should have the following characteristics to avoid the phenomenon of time-domain signal unsmoothness and explosion sound when the impact signals are superimposed: the window function values at the start and end time are 0; the window function is second-order derivable in other intervals except the start and end time.

[0115] Specifically, the impact signal is composed of a series of uniformly and discretely distributed impact units; the number of impacts in the simulation duration is obtained by multiplying the impact density by the total time length of the simulation sample; and the random numbers uniformly and discretely distributed in the simulation duration are generated according to the number of impacts.

[0116] The impact signal is composed of a series of uniformly and discretely distributed impact units, and the number of impacts N_pu in the simulation duration is obtained by multiplying the impact density dense_pu(n) by the total time length T of the simulation sample. n dense_pu(n)*T, n=1:M. n

[0117] Then, the random numbers R_t uniformly and discretely distributed in the simulation duration are generated. n,k k=1:N_pu, n=1:M. n

[0118] The white noise is filtered by using a band-pass filter with a freely set band-pass frequency range to generate a band-pass filtered signal, and then the signal is processed by using a window function and the random numbers uniformly and discretely distributed to generate impact noise with uniform and discrete random distribution.

[0119] Specifically, the impact unit window function is delayed by the number of impacts times to sum up to obtain an overall window function, wherein the delay times are the random numbers uniformly and discretely distributed in the simulation duration.

[0120] The impact noise simulation signal is generated by multiplying the band-pass filtered signal by the overall window function and then by the corresponding impact amplitude scaling coefficient.

[0121] There are mainly two methods for simulating the impact signal, the first method is to perform overall windowing on the band-pass filtered signal by using the window function with uniform and discrete random distribution to generate the impact noise simulation signal; and the window function of the impact unit is delayed by N_pu n times to sum up, and the delay times are R_t n,k , to obtain an overall window function:

[0122]

[0123] Then, the band-pass signal Sig_bp n is multiplied by the overall window function w_pu n (t) and then by the corresponding amplitude coefficient A_pu n ​​, the impulse noise simulation signal: Sig_pu_total is generated by superposition

[0124]

[0125] The method generates a time window with the same length as a single impulse time, delays and superimposes window functions by uniformly distributed random numbers to form an overall time window function, and then performs overall windowing on the band-pass noise signal to generate impulse noise.

[0126] Specifically, the band-pass filtered signal is multiplied by the impulse unit window function to obtain a single impulse unit. The single impulse unit is summed after being delayed for a number of impulses, to obtain N_pu uniformly distributed impulse units, wherein the delay time is a uniformly distributed random number in the simulation time. After the single impulse unit is multiplied by the corresponding impulse amplitude calibration coefficient, the impulse noise simulation signal is obtained by superposition and summation.

[0127] Among them, method two of simulating the impulse signal is to superimpose and synthesize the impulse noise simulation signal from the uniformly distributed impulse units;

[0128] The band-pass signal: Sig_bp n is multiplied by the window function of the impulse unit: w_unit n to obtain a single impulse unit:

[0129] Sig_unit n = Sig_bp n *w_unit n , n = 1:M

[0130] The impulse unit: Sig_unit n is summed after being delayed for N_pu n times, and the delay time is R_t n,k , to obtain N_pu n uniformly distributed impulse units, which are then multiplied by the corresponding amplitude coefficient and summed to obtain the impulse noise simulation signal: Sig_pu_total

[0131]

[0132] It can be understood that the impulse density is multiplied by the total sample time to obtain the total number of impulses, and the time delay of all impulse signals is generated by generating random numbers. In this example, a 10s long sample is to be generated, and according to Table 3, the frequency of impulse noise component 2 is 3 times / s, i.e. 30 impulse units need to be generated. The band-pass filtered signal 2 after windowing in 3.2 is copied 30 times, and 30 random numbers uniformly distributed in 10s are generated as the time delay of each impulse unit, to obtain all impulse unit distributions, as shown inFigure 16 and Figure 17 As shown in FIG. 6, the impact noise component 1 will generate 4 impact units within 10s, and 4 random numbers uniformly and discretely distributed within 10s are used to delay the 4 impact units respectively, and the distribution of the impact units of the impact noise component 1 is as shown in FIG. 7. Figure 18 , Figure 19 As shown in FIG. 8, the impact signal component 1 and the impact signal component 2 are multiplied by the corresponding amplitude coefficients and then added to synthesize the impact signal, and the FFT spectrum average result of the impact signal is as shown in FIG. 9. Figure 20 The FFT-time spectrum analysis result of the impact signal is as shown in FIG. 10, and it can be seen that the synthesized impact signal can well simulate the road impact noise component of the actual vehicle collected sample in the time-frequency characteristics. Figure 21

[0133] The method generates a time window with the same length as a single impact time, performs windowing on the band-pass noise signal to generate a unit impact noise signal, and then delays and superimposes the unit impact noise signal through uniformly and discretely distributed random numbers to generate the impact noise. The time window used by the method needs to meet the following characteristics: first, the window function values at the start and end time are 0, and second, the window function is second-order derivable in other intervals except the start and end time. The impact density of the road impact noise signal can be adjusted by setting the distribution number of the random number; the frequency characteristics of the road impact noise signal can be adjusted by changing the upper and lower limits of the band-pass filter; the time length and rising and decay characteristics of the impact unit can be adjusted by changing the window function; and the size of the road impact noise can be adjusted by changing the impact noise amplitude coefficient.

[0134] S114, add the wideband noise simulation signal, the narrowband noise simulation signal and the impact noise simulation signal to obtain a simulation signal of the in-vehicle noise of the uniform speed driving, save the simulation signal into a format playable by an electronic device, and use the simulation signal for playback and listening evaluation.

[0135] Specifically, due to the addition of the narrowband noise simulation signal and the impact noise simulation signal, the energy of the frequency band where the added signal component is located is improved, the improved energy information of the frequency band is fed back, and the energy of each frequency band of the synthesized simulation signal of the in-vehicle noise of the uniform speed driving is restored to the original sample level.

[0136] The method for restoring the energy of each frequency band of the synthesized simulation signal of the in-vehicle noise of the uniform speed driving to the original sample level further includes:

[0137] The energy of the corresponding frequency band in the wideband noise simulation signal is reduced by correcting the sound pressure amplitude calibration coefficient, the improved energy information is fed back, and the energy of each frequency band of the synthesized simulation signal of the in-vehicle noise of the uniform speed driving is restored to the original sample level through multiple iterations. ​

[0138] By adjusting the sound pressure amplitude calibration coefficient, the narrowband amplitude calibration coefficient and the impact amplitude calibration coefficient, the components of the simulated synthesized uniform speed driving vehicle interior noise are changed to generate different simulation samples;

[0139] The playback of the adjusted generated various samples is evaluated.

[0140] Among them, the simulation synthesis of the uniform speed driving vehicle interior noise is composed of wideband noise simulation signal, narrowband noise simulation signal and impact noise simulation signal;

[0141] The wideband noise simulation signal, the narrowband noise simulation signal and the impact noise simulation signal are added to obtain the simulation signal of the uniform speed driving vehicle interior noise:

[0142] Sig_combine=Sig_wb_total+Sig_nb_total+Sig_pu_total

[0143] The amplitude correction of the synthesized signal, due to the addition of narrowband signal and impact signal, the 1 / 3 octave energy of the added signal component is increased, the increased energy information needs to be fed back, and the amplitude coefficient A_wb of the wideband signal is corrected n , the corresponding 1 / 3 octave energy in Sig_wb_total signal is reduced, so that the 1 / 3 octave energy of the synthesized signal Sig_combine is restored to the original sample level, and this process can be completed by multiple iterations, as shown in Figure 22 ;

[0144] The analysis and verification of the simulation synthesis signal, the FFT analysis of the synthesized signal is shown in Figure 23 , it can be seen that the spectrum trend is basically consistent, and the main peak component is well simulated; the FFT-time time-frequency analysis of the synthesized signal is shown in ​ , it can be seen that the simulated synthesized noise signal and the noise signal collected by the real vehicle have similar time-frequency characteristics, and each component is well simulated.

[0145] The playback evaluation of the simulation synthesis signal, the simulated synthesized signal is saved into a format that can be played by electronic equipment for listening playback;

[0146] Among them, the simulated synthesized signal is saved into a format that can be played by electronic equipment, in this example, it is saved into a.wav format file, and professional acoustic analysis software in the computer is used for playback listening, and compared with the noise signal collected by the real vehicle, the auditory perception is consistent;

[0147] The application of the method for simulating the in-vehicle noise of uniform-speed driving vehicle, the parameters A_wb n , A_nb n , A_pu n of the wideband signal, the narrowband signal and the impact signal in the synthesized signal are adjusted to change the components of the simulated in-vehicle noise of uniform-speed driving vehicle and generate different simulation samples;

[0148] The playback and listening evaluation of the generated samples after adjustment can be used to identify the in-vehicle noise problem of uniform-speed driving vehicle, formulate the optimization target of the in-vehicle noise of uniform-speed driving vehicle, determine the optimization direction and predict the auditory sensation caused by the change of noise components. In this example, the amplitude of the road impact noise component of 80Hz-90Hz is reduced, the amplitude of the 1 / 3 octave band with the center frequency of 500Hz is increased, and the narrowband peaks near 200Hz, 400Hz and 1kHz are reduced. The optimized sample is simulated and generated. The FFT spectrum average result of the optimized sample is shown in ​ 、 ​ ;

[0149] The playback and listening of the optimized sound sample and the comparison and evaluation with the noise collected from the actual vehicle show that the overall auditory sensation is obviously improved, the road impact noise component is reduced, the mid-frequency region is more full, and the monotonous prominent component is basically eliminated. The simulated optimized sample can be used as the optimization target of the in-vehicle noise of uniform-speed driving vehicle of the example vehicle. The professionals in the field of automobile noise control can use the method to identify the in-vehicle noise problem of uniform-speed driving vehicle, formulate the optimization target of the in-vehicle noise of uniform-speed driving vehicle, determine the optimization direction and predict the auditory sensation caused by the change of noise components, and further work such as automobile development and design.

[0150] Although the embodiments of the present application have been shown and described, it is to be understood that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the present application, and the scope of the present application is defined by the appended claims and their equivalents.

Claims

1. A method of simulating in-vehicle noise of a vehicle cruising at a constant speed, characterized by, The method comprises the following steps: Collecting real vehicle uniform speed driving in-vehicle noise signal samples, determining the frequency range of the simulation signal, dividing the frequency range into a plurality of continuous frequency bands, calculating the average sound pressure of the in-vehicle noise signal samples in each frequency band, the FFT spectrum average result, and the FFT-time frequency analysis result; Randomly generating a first white noise signal, calculating the ratio of the average sound pressure of the in-vehicle noise signal samples in each frequency band to the average sound pressure of the first white noise signal in each frequency band, and obtaining the sound pressure amplitude calibration coefficient of each frequency band; The first white noise signal is respectively band-pass filtered in each frequency band, and then the sound pressure amplitude is calibrated by the corresponding sound pressure amplitude calibration coefficient to obtain a wide-frequency noise simulation signal; According to the FFT spectrum average result of the in-vehicle noise signal, the frequency lower limit, the frequency upper limit and the amplitude of a plurality of narrow-band components are determined; the narrow-band amplitude calibration coefficient is set according to the amplitude of each narrow-band component; a second white noise signal is randomly generated, the second white noise signal is filtered according to the frequency lower limit and the frequency upper limit of each narrow-band component, and then the amplitude is calibrated by the narrow-band amplitude calibration coefficient to obtain a narrow-band noise simulation signal; From the FFT-time frequency analysis result of the in-vehicle noise signal, the frequency lower limit, the frequency upper limit, the density, the single impact time and the impact amplitude of a plurality of road impact noise components are respectively confirmed; the impact amplitude calibration coefficient of the corresponding road impact noise component is set according to the impact amplitude; A third white noise signal is randomly generated, and the third white noise signal is band-pass filtered according to the frequency lower limit and the frequency upper limit of the impact noise component to generate a band-pass filtered signal with the same or similar frequency range as the impact noise; According to the density and single impact time of the impact noise component, the overall window function of the impact noise is generated, the band-pass filtered signal is overall windowed by the overall window function, and then the amplitude is calibrated by the impact amplitude calibration coefficient to generate an impact noise simulation signal; The wide-frequency noise simulation signal, the narrow-band noise simulation signal and the impact noise simulation signal are added to obtain the simulation signal of the uniform speed driving in-vehicle noise, and the simulation signal is saved in a format that can be played by an electronic device for playback and listening evaluation.

2. The method of claim 1, wherein, Collecting real vehicle uniform speed driving in-vehicle noise signal samples, determining the frequency range of the simulation signal, dividing the frequency range into a plurality of continuous frequency bands, and further comprising: Determining the simulation signal frequency range from the start frequency band lower limit and the end frequency band upper limit, or determining the simulation signal frequency range according to actual needs; The simulation signal frequency range is divided into a plurality of continuous frequency bands using integer or fractional octave frequency bands or fixed bandwidth frequency bands.

3. The method of claim 1, wherein, Randomly generating a first white noise signal, calculating the ratio of the average sound pressure of the in-vehicle noise signal samples in each frequency band to the average sound pressure of the first white noise signal in each frequency band, and obtaining the sound pressure amplitude calibration coefficient of each frequency band; The first white noise signal is respectively band-pass filtered in each frequency band, and then the sound pressure amplitude is calibrated by the corresponding sound pressure amplitude calibration coefficient to obtain a wide-frequency noise simulation signal, and further comprising: According to the one-to-one correspondence of a plurality of frequency band settings, a wide band pass filter is set, a first white noise signal is passed through each wide band pass filter to obtain a plurality of wide band communication signals, and each wide band communication signal is amplitude calibrated by a corresponding sound pressure amplitude calibration coefficient and then superimposed to obtain a wide frequency noise simulation signal.

4. The method of claim 1, wherein the method is a method of simulating in-vehicle noise of a vehicle cruising at a constant speed. According to the FFT spectrum average result of the in-vehicle noise signal, the frequency lower limit, the frequency upper limit and the amplitude of a plurality of narrow band components are determined; the narrow band amplitude calibration coefficient is set according to the amplitude of each narrow band component; a second white noise signal is randomly generated, the second white noise signal is filtered according to the frequency lower limit and the frequency upper limit of each narrow band component, and is amplitude calibrated by the narrow band amplitude calibration coefficient after superimposition to obtain a narrow band noise simulation signal, and the method further comprises: The number of the plurality of narrow band components is determined by the number of main narrow band components in the FFT spectrum average result of the in-vehicle noise signal and the simulation accuracy requirement; The narrow band band pass filter is designed according to the frequency lower limit and the frequency upper limit of each narrow band component; The second white noise signal is passed through the corresponding narrow band band pass filter to obtain a plurality of narrow band filter signals of the plurality of narrow band components; The plurality of narrow band filter signals are respectively amplitude calibrated by the respective corresponding narrow band amplitude calibration coefficient and then superimposed to obtain the narrow band noise simulation signal.

5. The method of claim 1, wherein the method is a method of simulating in-vehicle noise of a vehicle cruising at a constant speed. A third white noise signal is randomly generated, a band pass filter signal with the same or similar frequency range as the impact noise is generated by band pass filtering the third white noise signal according to the frequency lower limit and the frequency upper limit of the impact noise component, and the method further comprises: The band pass filter is set according to the frequency lower limit and the frequency upper limit of the impact noise component, and the third white noise is band pass filtered to generate a band pass filter signal with the same or similar frequency range as the impact noise.

6. The method of claim 1, wherein, The overall window function of the impact noise is generated, the band pass filter signal is overall windowed by the overall window function, and the amplitude of the band pass filter signal is calibrated by the impact amplitude calibration coefficient to generate the impact noise simulation signal, and the method further comprises: The impact unit window function of each impact noise component is set; The time length of the impact unit window function is the same as the single impact time; The window function values of the start and end time of the impact unit window function are set to zero; The window function is twice differentiable in other intervals except the start and end time.

7. The method of simulating in-vehicle noise of a vehicle cruising at a constant speed according to claim 6, characterized by, It comprises: The impact signal is composed of a series of uniformly distributed impact units; The impact number in the simulation time is obtained by multiplying the impact density and the total time length of the simulation sample; The random number is generated according to the impact number in the simulation time.

8. The method of claim 7, wherein the method is a method of simulating in-vehicle noise of a vehicle cruising at a constant speed. It comprises: The impact unit window function is delayed for the impact number of times respectively, and the overall window function is obtained by summing up the delay time, wherein the delay time is the random number uniformly distributed in the simulation time; The band pass filter signal is multiplied by the overall window function, and then multiplied by the corresponding impact amplitude calibration coefficient to generate the impact noise simulation signal.

9. The method of claim 7, wherein the method is a method of simulating in-vehicle noise of a vehicle cruising at a constant speed, characterized by, It comprises: The band pass filter signal is multiplied by the impact unit window function to obtain a single impact unit; The single impact unit is delayed for the impact number of times respectively, and the impact number of uniformly distributed impact units is obtained by summing up the delay time, wherein the delay time is the random number uniformly distributed in the simulation time; The single impact unit is multiplied by the corresponding impact amplitude calibration coefficient to obtain the impact noise simulation signal.

10. The method of claim 2, wherein the method is a method of simulating in-vehicle noise of a vehicle cruising at a constant speed. The wideband noise analog signal, the narrowband noise analog signal and the impact noise analog signal are added to obtain an analog signal of the uniform speed driving vehicle interior noise, the analog signal is saved in a format that can be played by an electronic device, and is used for playback listening evaluation. The analog signal of the synthesized uniform speed driving vehicle interior noise is added with the narrowband noise analog signal and the impact noise analog signal, so that the energy of the frequency band where the added signal component is located is increased, the increased energy information is fed back, and the energy of each frequency band of the synthesized uniform speed driving vehicle interior noise analog signal is restored to the original sample level. The energy of each frequency band of the synthesized uniform speed driving vehicle interior noise analog signal is restored to the original sample level. The energy of each frequency band of the synthesized uniform speed driving vehicle interior noise analog signal is restored to the original sample level. The energy of each frequency band of the synthesized uniform speed driving vehicle interior noise analog signal is restored to the original sample level. The energy of each frequency band of the synthesized uniform speed driving vehicle interior noise analog signal is restored to the original sample level. The energy of each frequency band of the synthesized uniform speed driving vehicle interior noise analog signal is restored to the original sample level. The energy of each frequency band of the synthesized uniform speed driving vehicle interior noise analog signal is restored to the original sample level. The energy of each frequency band of the synthesized uniform speed driving vehicle interior noise analog signal is restored to the original sample level. The energy of each frequency band of the synthesized uniform speed driving vehicle interior noise analog signal is restored to the original sample level. The energy of each frequency band of the synthesized uniform speed driving vehicle interior noise analog signal is restored to the original sample level. The energy of each frequency band of the synthesized uniform speed driving vehicle interior noise analog signal is restored to the original sample level.

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