Stabilization method and sound quality control method for volume and sound quality control of road noise

Abstract

To provide a sound quality volume control method for a playback device for a vehicle that can cope with strong noise by stably controlling a range of 43 dB in total, which includes a 20 dB fluctuation in average intensity depending on the running speed, a 10 dB response to road surface roughness, and a 13 dB response to the intonation of the strength of the input playback signal and the intonation of the clear component strength, thereby coping with strong noise and meeting market demands. [Solution] The method includes detecting driving noise using the vibration acceleration of the vehicle structure rather than sound pressure, offsetting the coupling path with a signal obtained by multiplying the output strength of the simulated coupling path by a safety factor to address uncertain factors resulting from errors in the coupling path that simulates the coupling path from playback to detection, correcting the intonation of the strength of the playback signal and the intonation and volume sound quality of the clear voice component of the playback signal using the degree of driving vibration acceleration strength after offsetting, and detecting the strength of the announcement signal and music signal after ensuring the range and stability of control, and selecting sound quality suitable for both announcements and music depending on the strength.

Description

[Technical Field]

[0001] Control stability of systems with closed loops. Adaptive Filter Environmental Sound Control [Background technology]

[0002] Environmental noise-responsive volume and sound quality control Acoustic Signal Processing Vibration of the vehicle body during travel Car driving noise

[0003] The terms and symbols defined in the claims shall be used in the specification as well. Unless otherwise specified, descriptions of running noise and running vibration acceleration are in agreement. below, Considerations 1 to 14 in the development process of this proposal are related to background technology.

[0004] The following are considerations 13 and 14 in the development process of this proposal: Patent application No. 2023-184376 has made it possible to achieve a volume and sound quality control method that can respond to a wide range of noises and provide stable control. Through practical testing using this method, As a result of confirming the imperfection of sound quality in relation to noise, This adds further improvements to sound quality and to the sound quality control method that accompanies the sound quality improvements.

[0005] Considerations in the development process of this proposal: Part 1. Current status of measures to combat running noise The first step in reducing noise from passenger cars is to use sound-absorbing materials. In other words, the most effective way to reduce noise is to convert as much vibration energy as possible into heat energy. However, there is a trade-off between noise reduction performance and weight and cost, and compromises must be made. Lightweight and low-cost vehicles tend to be prioritized, especially in smaller cars. On the other hand, there are methods for actively suppressing running noise, but in practice, the maximum reduction is about 3 dB up to 500 Hz, which is not a level of performance that will be well received in the market. As a result, for cost-conscious cars, driving noise is unavoidable, but at least the interior noise is When listening, sound quality volume control that matches the road noise is generally used.

[0006] Considerations in the development process of this proposal: Part 2. Main factors behind variations in running noise As shown in Figure 1, even at the same driving speed, the noise intensity is almost the same for small and medium-sized vehicles, with a variation of about 20 dB. This variation is due to road conditions, engine speed, and load conditions. Although we do not have a complete grasp of the market situation, many vehicle models have volume and sound quality control that depends on driving speed instead of driving noise. From the example of actual measurements in Figure 1, it can be seen that the method adapted to the running speed cannot cope with a variation of 20 dB at the same running speed.

[0007] Considerations in the development process of this proposal. Part 3. Relationship between input regenerative signal strength and running noise intensity FIG. 2 is a diagram illustrating the relationship between the playback signal strength and the running noise. If the road noise is louder than the playback signal, you will not be able to listen to whatever the signal is. If the playback signal has large fluctuations in intensity, the playback sound may be too loud and remain in the noisy range even when the volume is increased. There are some weak and inaudible ranges, and in the case of announcements, it is noisy but the content cannot be heard. This causes the following inconvenience. By making the intensity constant, it is possible to adjust the playback sound intensity to a level that allows the content to be heard without increasing the maximum intensity more than necessary.

[0008] Considerations in the development process of this proposal: Part 4. Modulation of the intelligible component strength of announcement signals Figure 3 shows an example of the inflection of the intelligible component strength extracted from a sample of a relatively low-intelligibility announcement signal and how to address it. The figure shows an example of correction for 8 ddB. Experimental confirmation has shown that the appropriate maximum correction amount for the clear component intensity is approximately 10 dB. In this example, it can be seen that the clear component intensity fluctuates greatly. The weak intensity portion of the clear component can be stretched and made constant. This problem may seem like it could be solved by simply increasing the volume, but the strength of the signal itself and the strength of the clear components are not necessarily linearly correlated. Increasing the strength uniformly overemphasizes unnecessary components, which can be unpleasant, so simply increasing the volume cannot solve the problem.

[0009] Considerations in the development process of this proposal: Part 5. Overall required amount of intensity correction for the read signal The average noise intensity varies by 20 dB up to 110 km / h. If the input signal strength change range is 10 dB and the clear component intonation range is 10 dB, then Both together are 20dB. However, the intonation and the intensity intonation of the clear component are not completely independent. Due to common factors, 13 dB is statistically the practical required range. The range of variation in running noise intensity due to road surface conditions is +-10dB from the average. Roughly speaking, a total intensity control range of 20dB + 10dB + 13dB = 43dB is required. The essence of this proposal is that a stable and controllable intensity range of approximately 43 dB is required.

[0010] Considerations in the development process of this plan: 6.43dB intensity control The figure of 43dB was obtained through field experiments leading up to the proposal and through incorporating the product into test sales, and is not a universal figure. However, because it is an empirical figure that combines issues with multiple complex factors, it is a figure that is meaningful enough for product design. Even if extremely precise laboratory-level acoustic signal processing were possible, it is not easy, according to common sense, to ensure the accuracy and stability of controlling the strength of a closed-loop system within a 43 dB range. This is clear when we look at the current state of this type of functionality in ordinary compact cars, compact hybrid cars, and compact electric vehicles as of 2023.

[0011] Considerations in the development process of this proposal Part 7. How to achieve the target value of 43dB There are three ways to deal with this 43dB noise: First, a road noise detection method that significantly reduces the closed-loop intensity gain caused by the coupling of the regeneration system and the detection system. Second, accurate and significant removal of the intensity of the reproduced sound component that is mixed into the detected signal intensity of driving noise. Third, the removal of instability factors caused by the discrepancy between the simulated coupling path and the actual coupling path.

[0012] Considerations in the development process of this proposal. Part 8. Relationship between vehicle body vibration acceleration and running noise Figure 4 shows the device housed in a DIN cabinet and mounted on a printed circuit board. The following shows an example of actual measurements of the relationship between the output strength of an acceleration sensor and noise intensity for each frequency band. Although there is a variation of about +-2dB in the relationship between the accelerometer and noise in all frequency bands, it shows that there is generally a linear correlation. In other words, this shows that the vibration acceleration of the vehicle structure can be used as a substitute for the output of the air microphone.

[0013] Considerations in the development process of this proposal: Part 9. Strength of the connection between the speaker and the accelerometer The degree of coupling between the vibration acceleration of the vehicle body and the original playback signal is extremely important. Figure 5 shows a comparison of actual measurements of the closed-loop coupling strength between a microphone and an acceleration sensor. As a result, the coupling from the accelerometer is 13dB to 14dB less than that from the microphone. In other words, by substituting the vehicle acceleration for the running noise, the closed-loop coupling can be improved by 13 dB.

[0014] Considerations in the development process of this proposal Part 10. Running noise mixed with regenerated signal components Removal of original reproduced signal component strength from detected signal strength Figure 6 is a quote from Table 1 of Patent Application No. 2017-077577. Let X be the original playback signal component and Y be the detected environmental noise. This table shows that the intensity of the original reproduced component contained in the noise can be separated from the noise intensity with an accuracy of 0.05%. This table shows theoretical values. The accuracy in actual operation is It is determined by the difference between the simulated coupling path characteristic that generates the cancellation signal from the original playback signal and the coupling path in operation. Since this difference can be contained within an error or drift of about 10%, the actual cancellation amount that can be achieved is about 20 dB.

[0015] Considerations in the development process of this proposal. Part 11. Error countermeasures for simulated coupling paths In relation to the error described in No. 10 above, the stability of the control system must be given top priority. Therefore, there is a possibility that the control system may enter an unstable region due to a deviation from the actual state of the control system. Correction is applied by multiplying the output strength of the simulated coupling path by a coefficient greater than 1. Furthermore, fixed vibration intensity components are removed as necessary. By correcting the coefficient, a stable control range of approximately 20 dB can be ensured.

[0016] Considerations in the development process of this proposal Part 12. Comprehensive improvements Considerations 9, 10, and 11 are: This shows that it can be used to improve the control range by a total of 13dB + 20dB + 10dB = 43dB. Although none of these values ​​have theoretical universality, they have been experimentally verified. Abstract theory is completely useless for designing practical devices with this kind of functionality, We guarantee that the verification results from actual measurements can be applied to product design. That is, by utilizing and combining known detection methods and various signal processing techniques, This enables high-performance, wide-ranging volume control over driving noise versus sound quality that has not been achieved before.

[0017] Considerations in the development process of this proposal Part 13. How to improve sound quality and how to control it Although it has become possible to control the volume of sound quality in a wide range of driving noise, the driving tests revealed that there is a sense of incongruity in the sound quality of announcements and music in noisy environments, and that different sound quality controls are required for each. The additional function required is a combination with a function for detecting the degree of SM. The essence of this proposal is In addition to the already available wide-range driving noise vs. sound quality volume control method (Patent Application No. 2023-184376), we will also make it dependent on the degree of announcement tendency and music tendency, i.e., SM degree. By continuously controlling the mix ratio from full announcement to full music, This enables higher quality sound reproduction in noisy environments.

[0018] Considerations in the development process of this proposal Part 14. How to improve the quality of music linked to noise moreover, A filter for music in strong noise conditions works just as well in weak noise conditions, but a filter with a first-order low boost and first-order high boost has little independence from the midrange, and the emphasized high range sounds a bit lacking in definition in relation to the midrange, or the midrange sounds are too strong. In addition, the widely used second-order IIR bandpass filter has a pole, and the bass sound quality of this proposal has a high gain of 30 dB. Therefore, if the parameters are changed while the system is running, The filter itself generates unstable behavior such as oscillation, making it unsuitable for high-speed continuous control. Although it is a known method, For low boost, the output signal of a filter with two connected primary high cuts is multiplied by an amplification coefficient, and the resulting signal is used as a bass emphasis signal for music. For high boost, the output signal of a filter with two connected primary low cuts is multiplied by an amplification coefficient, and the resulting signal is used as a treble emphasis signal for music. a signal obtained by adding the bass emphasis signal for music and the treble emphasis signal for music to each other is used as a sound quality emphasis signal for music; For music emphasis signals, By applying two types of signals, a correction control signal corresponding to the noise intensity and a signal corresponding to the intensity of the original playback signal, the system is controlled to deal with both noise and to prevent saturation in the playback system. An optimal music enhancement signal is generated, the sign of this signal is inverted, and added to the original signal. The filter characteristics and amplification coefficients for the bass and treble are determined by design. [Prior art documents] [Non-patent literature]

[0019] Although there is a large amount of literature, it is all purely theoretical and does not provide any useful information to solve the many challenges faced when creating practical products. Considerations 1 to 12 in the development process of this proposal are reference materials that replace non-patent literature. [Patent documents]

[0020] Patent application 2018-70016: Acoustic system, sound reproduction device, and sound reproduction method Patent application 2015-149105 In-vehicle sound reproduction device Patent application 2011-52671 In-vehicle sound reproduction device Patent application 2007-2-1622 Automatic sound quality control device and integrated circuit Patent application 2002-149930 Audio playback device Patent application 2001-188599 Audio signal decoding device Patent application No. Hei 10-323316 All of the above are There is no description of the vibration acceleration intensity of the vehicle structure. There is no description of a method for subtracting the combined component of the reproduced signal strength from the detected vibration acceleration strength with high accuracy for correction. There is no description of the overall required control range of the input reproduction signal strength, which is related to the range of inflection of the input reproduction signal strength, the range of fluctuation of the road noise strength, and the range of inflection of the clear component strength, and how to solve this problem. is raised. This is in light of the issue of improving the current control range of 43 dB. It can be said that the content of this case is essentially different from that of the present case. Patent application 2017-077577 Noise spectrum detection method and noise volume control method A method for accurately detecting noise intensity from a signal containing a mixture of noise and a reproduced sound, comprising: It is not about improving the controllable range of the overall absolutely necessary amount of road noise.

[0021] Patent application 2023-184376 Stabilization method for controlling volume and sound quality of driving noise This relates to a method for stabilizing control over a wide range, which is a preliminary step to the present invention. There is no description of the proposed function for detecting the degree of SM or the function for changing the mixing ratio of announcement signals and music signals depending on the degree of SM. Patent Application No. 2018-093666 Method for detecting the degree of speech and non-speech This is a function for detecting the degree of SM in the input playback signal, and is necessary for this invention. Summary of the Invention [Problem to be solved by the invention]

[0022] Challenge 1 When controlling the sound quality and volume in response to the driving noise inside a moving vehicle, In particular, when the signal being reproduced is a voice, the voice cannot be heard if the strength of the voice changes in a weak range. If there are too many interruptions, it becomes difficult to hear the whole thing. If you turn up the volume until you can hear it, the noise level will be higher in the range where the driving noise intensity is already high. The volume becomes so intense that it becomes unbearable to listen to, and as a result, you cannot turn up the volume. The same applies when the playback signal is music.

[0023] Challenge 2 By reinforcing the weak intensity range of the input playback signal, which has fluctuations in intensity, the intensity becomes uniform and becomes easier to hear. However, there is a coupling path from the playback speaker to the road noise detector, so the system forms a closed loop. Increasing the amplification level creates a positive feedback effect on the closed loop strength coupling, Intensity control becomes unstable. Because the intensity control system does not have instantaneous signal coupling, there is no oscillation in a normal linear system, but even with the coupling of intensity states, positive feedback can act under certain conditions. This means that there are limits to the control performance of volume and sound quality in response to road noise.

[0024] Challenge 3 Although Patent Application No. 2023-184376 is a method sufficient to achieve satisfactory control over a wide range of 43 dB, actual driving tests confirmed that it had a drawback in that it was not possible to achieve optimal sound quality for both announcement signals and music signals when controlling sound quality in response to noise.

[0025] Challenge #4 Actual driving tests using the method of Patent Application No. 2023-184376 confirmed that when a wide range of playback signals corresponding to weak to strong noises is controlled using only the method of Patent Application No. 2023-184376, the volume of the mid-range sounds is strong in music signal playback, and there is no sense of sharpness in the relationship between the ultra-low and ultra-high mid-range sounds. Furthermore, if a commonly used second-order IIR bandpass filter is used to create a sense of contrast between low and high tones, the filter will have a pole, and since the bass sound quality generated in this proposal requires a high gain of 30 dB, changing the parameters while the system is operating will cause the filter itself to oscillate and other unstable operations, making it unsuitable for high-speed continuous control. [Means for solving the problem]

[0026] Combining the following functions:

[0027] Method 1: To detect running noise, use the running vibration acceleration of the vehicle body structure instead of sound pressure. Fig. 2 shows the measured correlation between running noise intensity and vibration acceleration intensity of a part of the car body. A linear correlation between vibration acceleration intensity and running noise intensity is observed in all frequency bands. By replacing running noise intensity with vibration acceleration intensity, an intensity control range of approximately 13 dB is ensured.

[0028] Means 2: By subtracting the original playback signal component strength included in the detected signal strength of vibration acceleration, Extracts accurate vibration acceleration intensity that has a first-order correlation with running noise.

[0029] Means 3. For the error of the simulated coupling path, A correction factor R greater than 1 is applied to the output signal strength of the simulated coupling path.

[0030] Means 4. With the detected and calculated accurate and safe corrected driving vibration acceleration intensity value, Corrects and equalizes fluctuations in the intensity of the input playback signal. If necessary, the intonation of the clear component when the input playback signal is an announcement is corrected and made uniform.

[0031] Means 5 Accurate and safe corrected driving vibration acceleration intensity detected and calculated A combination of precise signal processing ensures a stable control range of 43dB. They are, The degree of inflection of the reproduced signal strength is corrected in accordance with the degree of the corrected running vibration acceleration strength. The degree of inflection of the intensity of the clear component of the reproduced signal is corrected in accordance with the degree of intensity of the post-correction running vibration acceleration. The volume and tone intensity of the reproduced signal are corrected according to the degree of intensity of the corrected running vibration acceleration. It is a combination of:

[0032] Means 6 A function for detecting whether the input playback signal is an announcement signal or a music signal is incorporated. The gray zone, including natural environmental noise from complete announcements to complete music, is continuously measured numerically, and the SMD degree is calculated based on the numerical value. Controls the mix ratio between the announcement filter output and the music filter output.

[0033] Means 7 The input signal is passed through a filter consisting of two first-order high-cut filters connected in series, a signal obtained by multiplying the output signal by an amplification factor determined by design; The input signal is passed through a filter consisting of two first-order low-cut filters connected in series, a signal obtained by multiplying the output signal by an amplification factor determined by design; and generate a music quality enhancement signal. For music quality enhancement signals, Music sound quality generation function that corresponds to road noise and Saturation suppression function to prevent the playback system from becoming saturated and generate a coefficient Klef that depends on both The music quality enhancement signal is multiplied by klef, the sign of which is inverted, and the resulting signal is added to the input signal to generate the music quality signal. [Effects of the Invention]

[0034] Effect 1 of Method 1 By using vibration acceleration of a part of the vehicle body that has an intensity correlation with running noise instead of sound, Reduces the coupling between the playback system and acceleration detection function. This reduction effect is 13dB to 14dB in actual measurements.

[0035] Effect 2 of Method 2 PK(Y)=PK(X+Y)-P(X) By this signal processing, the original reproduction signal component intensity included in the detection signal intensity is accurately removed. Theoretically, this effect is 74 dB, but in reality, it is approximately 20 dB, since an error of approximately 10% is estimated due to the difference between the simulated coupling path and the actual coupling path.

[0036] Effect 3 of Method 3 P(X+Y)-R*P(X) or P(X+Y)-R*P(X)-Bias A proportionality coefficient R greater than 1 such that By applying a fixed bias as needed, This can eliminate the cause of instability in the control system due to errors contained in the strength of the detected signal.

[0037] Effect 4 of Method 4 The weak intensity portion of the input playback signal having intensity fluctuations is stretched and corrected. The proper maximum range of extension can be improved by 10dB.

[0038] Effect 5 of Method 5 The volume and sound quality of the playback signal, with its intensity tones made uniform, is corrected in accordance with the intensity of the detected and processed driving vibration acceleration, with a correction range of approximately 20 dB.

[0039] Effect 6 of Method 6 Both the clarity required for announcement signals and the rich sound quality from ultra-low to ultra-high frequencies required for music signals can be set independently.

[0040] Effect 7 of Method 7 It can reproduce music with a good balance between the ultra-low and midrange frequencies, and the ultra-high and midrange frequencies, from low to high noise levels, while avoiding saturation of the playback system under any operating conditions, including input signal, playback volume, and playback sound quality.

[0041] Overall effect of measures 1 to 7 The required range of 43 dB for controlling the intensity of the input playback signal can be secured, enabling stable control. Across the entire noise range from weak to strong The announcements can be adjusted to a high level of clarity suitable for announcements, while the music can be adjusted to a realistic level suitable for music. Both can be adjusted independently, and are saturation-free.

[0042] Combining multiple methods is the essence of this invention. [Brief explanation of the drawings]

[0043] [Figure 1] Actual measurement examples of the relationship between driving speed and driving noise: (a) for a small vehicle with hearing weighting curve A, (b) for a medium-sized vehicle without hearing weighting [Figure 2] An example diagram showing the relationship between the intonation of the announcement signal strength and road noise. (a) The relationship between the intonation of the announcement playback signal strength and road noise. (b) The relationship between the intonation of the playback signal and road noise when the announcement playback signal strength is increased in a road noise environment. (c) The relationship between the playback signal and road noise when the intonation of the announcement playback signal strength is kept constant in a strong road noise environment. [Figure 3] An explanatory diagram of the modulation of the clear component strength of an announcement signal. (a) Changes in the clear component strength of an example of an announcement signal with poor intelligibility. (b) An example of a signal with improved modulation of the clear component strength of Figure 3(a). (c) An example of the characteristics of removing unclear components and emphasizing clear components. (d) An outline of an example of an algorithm for signal processing of clear components. [Figure 4] Actual measurement example of the correlation between the output strength of an acceleration sensor and noise intensity for each frequency band [Figure 5] Actual measurement example of the closed-loop coupling strength between an acoustic microphone and an accelerometer. (a) Comparative measurement results of the closed-loop coupling strength depending on the type of sensor. (b) Block diagram of the measurement method for the measurement results in Figure 5(a). [Figure 6] A theoretical numerical table showing that accurate vibration acceleration can be calculated by subtracting the playback sound intensity included in the detected vibration acceleration. Excerpt from Patent Application 2017-077577 [Figure 7]Graph showing the characteristics of running noise control based on running vibration acceleration intensity [Figure 8] Illustrative diagram of volume and sound quality correction for driving vibration acceleration intensity [Figure 9] Graph showing the closed-loop gain margin of the control system based on the intensity of running vibration acceleration [Figure 10] Block diagram for explaining the present invention [Figure 11] Examples of statistical data of signals required for detecting the SM degree and how to use the SM degree: (a) Amplitude distribution when the mixture ratio of a perfect announcement and perfect music is changed; (b) Amplitude distribution when the mixture ratio of a perfect announcement and white noise is changed; (c) Amplitude distribution when the mixture ratio of a perfect announcement and crisp guitar music is changed; (d) Example of characteristics of the relationship between the SM degree and the mixture ratio. [Figure 12] (a) Block diagram of the function that synthesizes the sound quality of a music signal. (b) Example of the characteristics of a music signal that change depending on the conditions of road noise and output intensity. BEST MODE FOR CARRYING OUT THE INVENTION

[0044] Remanufacturing equipment for small and medium-sized vehicles where weight reduction is essential [Industrial Applicability]

[0045] Acceleration sensor built into electronic circuit printed board Software for audio processors. [Example]

[0046] Like sound systems, they consist of hardware and software that are evaluated by human senses. Many of the evaluation items for industrial products are evaluated using adjectives. In such cases, if you must express a function numerically, use the numbers with a prefix such as "approximately" or "approximately". The numerical values ​​used in the explanation of this proposal are modifiers such as "roughly" and "approximately," but these are equivalent to "statistically" and do not detract from the essence of this proposal. The evaluation of sound quality is a comprehensive assessment based on human senses, and if, for example, some factor changes negatively by 1 dB, some of the various factors will be slightly degraded. In the process of arriving at the final proposal, try out one example of an improvement plan, and if it is insufficient, propose further improvements. By layering the typical cut-and-try method, There is a reason why the scope has been expanded. The essence of this proposal is The total necessary control range is about 43dB. The required control amount for both intensity and clarity is approximately 13 dB. The required control amount is approximately 20 dB according to the average value of the speed-dependent component of running noise. The required control amount for driving noise according to road surface conditions, engine speed and load is approximately 10 dB. The method to satisfy the required control range of about 43 dB in total, the breakdown of which is as follows: The control range that can be improved by substituting running vibration acceleration for running noise is approximately 13 dB. By cutting off the closed loop coupling path of the control system, the control range can be improved by approximately 20 dB. By eliminating the error factors between the actual coupling path and the simulated coupling path, the control range can be improved by approximately 10 dB. In both cases, the required amount is met by the sum of multiple factors and the resulting improvement. The drawings are explained below.

[0047] Figure 1 shows an example of actual measurements of the relationship between running speed and running noise. The horizontal axis is the driving speed in [km / h]. The vertical axis is the sound level meter reading in [dB]. Running Speed ​​is the running speed. In both cases, the measurement method was to record the speedometer readings and sound level meter readings while driving. By increasing the number of measurements, the statistical reliability of the data is ensured. The vertical axis is dB logarithmic, and the horizontal axis is km / h, so it is proportional, and so To see the correlation between the vertical and horizontal axes, check the running noise for every doubling of running speed, for example. Figure 1(a) shows the results for a small car. Road Noise (A-Curve) is a graph showing the relationship between driving speed and road noise. The hearing weighting is A. Since the noise level has been measured after removing low-frequency components, the noise level appears lower than it actually is. A Small Class Car indicates that the specimen is an example of a small car. Figure 1(b) shows the results for a medium-sized vehicle. Road Noise (Proportional) is a graph showing the relationship between driving speed and road noise. There is no auditory correction. Since this is a noise level that does not remove low-frequency components, the number shown is higher than the actual level. A Middle Class Car indicates that the specimen is an example of a medium-sized car. There are three items common to Figure 1(a) and Figure 1(b), which are the essence of this proposal. First, the relationship between running speed and running noise is, on average, almost linearly correlated. Secondly, the fluctuation range of running noise at the same speed is roughly 20dB, so it can be said that it fluctuates up or down by +-10dB from the average trend at that speed. Third, this variation depends mainly on the road surface condition and engine noise due to engine load.

[0048] FIG. 2 is a diagram illustrating an example of the relationship between the inflection of the reproduced signal intensity and the running noise. RNL indicates the driving noise level, Weak indicates the range in which the strength of the reproduced signal is too weak compared to the noise, Strong indicates the range in which the strength of the reproduced signal is too strong compared to the noise, and Stable indicates the range in which the strength of the reproduced signal is balanced compared to the noise. Generally, playback signals have intensity fluctuations. In particular, the intensity fluctuations of announcement signals vary from person to person. The intensity of a good announcer's voice is small in terms of conveying information, but In normal conversation situations, the voice expresses emotions and has a strong intonation. Especially when the road noise is loud, whether it is music or announcements, the intensity is low. I can't hear anything at all. Therefore, if the intensity is increased to an audible level, the volume will be so intense that it will interfere with driving at high intensity ranges. It is well known that the best countermeasure is to make the intensity of the reproduced signal uniform. The explanation in Figure 2 shows the problem that when correcting the weak intensity part, the playback signal in that range must be amplified. Roughly speaking, about 10 dB of reinforcement is required, but if the playback device Since the closed loop has acoustic coupling, the stronger the reinforcement, the more unstable the control system becomes. The necessity of approximately 10 dB of correction for intensity fluctuations is the essence of this proposal.

[0049] FIG. 2(a) shows the relationship between the intonation of the playback signal strength of the announcement and the running noise. If road noise becomes louder than the playback sound, the listener will need to turn up the volume.

[0050] Figure 2(b) shows the effect of increasing the playback signal strength of the announcement in a noisy driving environment. The graph shows the relationship between the inflection of the playback signal and the running noise. When the noise is strong, the reproduced sound may be both too loud and too soft depending on the inflection of the intensity.

[0051] FIG. 2(c) shows the relationship between the playback signal and road noise when the intonation of the announcement playback signal intensity is kept constant in a strong road noise environment. In low noise conditions, the intonation-corrected signal sounds strange, but in high noise conditions, this strangeness is reduced, and being able to hear the entire range is actually a good result for listening. In particular, when the content of the playback signal is news or talk, a balance must be struck between maximizing the audibility of the content and minimizing the annoyance caused by the volume.

[0052] FIG. 3 is an explanatory diagram of the clear components of the announcement signal and their intonation. The strength of the clear component of the announcement depends on the strength of the original announcement signal, Regardless of the strength of the announcement signal, it also depends on other factors. The strength of the intelligible component varies regardless of the loudness of the voice, depending on various conditions such as personality, posture at the time of speaking, and emotion. When the noise level increases, the audibility decreases in the range where the intelligible component intensity is weak, even with a reproduced sound whose intensity has been equalized. To improve the audibility in a noisy environment, it is necessary not only to equalize the intensity but also to equalize the intelligible component intensity. This, along with the techniques used, is well known. The important point in relation to this proposal is that roughly 10 dB of clear component intensity correction is required. The maximum calculation for the reinforcement of the reproduced sound and clear component intensity is 20 dB, but due to common factors, the actual amount can be estimated to be about 13 dB for both. Clearness Element in UN-Clear Announcement & Improvement The figure shows the strength of the clear component of an unclear announcement signal for about 20 seconds and explains how to improve it. Required Level is the required level of intelligibility. Signal having big dispersion in clearness shows an example where the clear component has a large dispersion. Improved Clearness shows an example of improvement in the intonation of the strength of the clear component of the test signal. Clearness is improved by 3 points to 21 points in the required level by 8 dB of clearness conditioning. This shows that the number of points exceeding the required intensity of clear components has improved from 3 to 21.

[0053] FIG. 3(a) shows the change in the intelligible component intensity of an example of an announcement signal with poor intelligibility. The signal is the clear component extracted from the original playback signal. There are three points above the required clarity intensity.

[0054] Figure 3(b) shows an example of a signal in which the intonation of the clear component intensity in Figure 3(a) has been improved. There are 21 points above the required clarity intensity.

[0055] FIG. 3(c) is an example of the spectral distribution of the intelligibility component. Clearness Element indicates that the diagram is a description of a clarity element. The horizontal axis is frequency and the vertical axis is spectrum intensity. Not Needed Elements are the pitch components of the announcement signal that are not necessary for clarity. The Needed Element is the band of vowels and consonants in the announcement signal that are necessary for intelligibility. Pitch components are removed, and vowels and consonants are emphasized. Generally, There are signals in which the intensity of the intelligible components is uniformly insufficient in the band required for intelligibility, and signals in which the intensity of the intelligible components fluctuates for some reason. By compensating for the reduced clarity caused by these factors, It is reproduced as an announcement signal that is easy to hear even in the presence of road noise.

[0056] FIG. 3(d) shows an outline of the algorithm for generating the clarity component. Reject Pitch Element is a process to remove pitch elements that are not necessary for intelligibility. Extraction Clearness is the process of extracting clarity components. Amplify Clearness is the process of amplifying clarity components. Align Clearness Element is an intonation correction process for the clarity element. is.

[0057] Figure 4 shows an example of measurements of the relationship between the output strength of the acceleration sensor and noise intensity for each frequency band. Since both the vertical and horizontal axes are converted into detected voltage, the figure shows that the detected acceleration and running noise have a linear correlation with an error range of +-2 dB. This shows that the detected signal strength of the vibration acceleration of the mechanical parts connected to the car body can be substituted for the running noise strength. This is one of the essential points of this proposal. Correlation between mechanical vibration & noise SPL is The figure shows an example of actual measurements showing the correlation between vibration acceleration and running noise. Horizontal; Acceleration on the body [mV], Vertical; Noise SPL at the driver's location [mV] is, The horizontal axis of the figure represents the vibration acceleration of a part of the car's mechanism, expressed in units of the detector's output voltage [mV]. The vertical axis of the figure represents the driving noise from the driver's seat, expressed in units of the detector's output voltage [mV]. 32Hz, 63Hz indicates that the frequency range is from 32Hz to 63Hz. Measurement results for seven frequency bands up to 4000Hz are shown.

[0058] Figure 5 shows an example of measurements of the closed-loop coupling strength in a playback system between an acoustic microphone and an acceleration sensor. By substituting running vibration acceleration for noise, it is possible to improve the control range by approximately 13 dB. The use of vibration acceleration to detect running noise is the essence of this proposal. Regarding the degree of coupling of the closed loop, the reality is that noise detection using a microphone is not sufficient to stabilize the control system to accommodate the required control range. Although actual measurement data for each car audio system has not been verified, as of 2025, It can be said that there is no car, at least small or medium-sized, that has been evaluated as meeting users' potential needs when it comes to features to deal with driving noise. One of the important factors is the sensor for the running noise. In the explanation of Figure 4, we showed the results of measurements that show a linear correlation between the running vibration acceleration and the running noise, but it is essential that the acoustic coupling from the speaker to the acceleration sensor is much weaker than that of the microphone.

[0059] Sample Car: Middle Class indicates that the sample car is a medium-sized car. Pilot Signal: 20---100Hz Random Noise is the pilot signal for measurement. Indicates random noise in the range of 20Hz to 100Hz. Sensor: The vertical columns of the table indicate the sensor type, The vertical columns of the table indicate the location of the sensor. The vertical column of the table shows the signal output to the howling point, which is the voltage detected by the sensor just before the closed loop howls due to the gain adjustment of the power amplifier. The unit is [mV]. Improved Gain Ratio [dB] is the vertical column of the table showing the magnification of the improvement in the coupling strength of the closed loop. The numbers in parentheses indicate the dB conversion of the multiplier. Microphone Non-Porlar is a microphone with a non-directional sensor. Acceleration Vertical-Polar: The sensor detects acceleration in the vertical direction. Driver's Head Rest: The measurement point is the head rest of the driver's seat. Din-Box Frame: The measurement point is the frame of a DIN box. PCB installed in the DIN Box Cabinet indicates that the measurement point is housed in a DIN box. Printed board in the cabinet, Microphone is a microphone, Acceleration is an acceleration sensor, Switch is the sensor selector switch, M, N, A indicate whether the switch is on the microphone side, neutral side, or acceleration sensor side, respectively. Sensor Amp is an amplifier circuit for the sensor output signal. OSC 20-100Hz Random Noise: The measurement signal is random noise in the range of 20Hz to 100Hz. MIX is addition, Power Amp is a power amplifier with adjustable gain. Speaker L and Speaker R are the left and right playback speakers, V is a voltmeter for measuring the output level of the measurement signal. is. A fixed bias signal is added to the acceleration signal, and the degree of coupling is obtained by reading the voltmeter at the bias signal level at the feedback point. The reference value for a microphone is 200 mV, and 850 mV and 1100 mV indicate that the coupling is 4.25 times (12.6 dB) and 5.5 times (14.8 dB), respectively. Figure 5(a) shows the comparative measurement results of the closed-loop coupling degree depending on the type of sensor. FIG. 5(b) is a block diagram of a measurement method for the measurement results of FIG. 5(a).

[0060] FIG. 6 is a theoretical numerical table showing that accurate vibration acceleration can be calculated by subtracting the reproduced sound intensity included in the vibration acceleration. The essence of this proposal is that the control range can be improved by approximately 10 dB by using a theoretically accurate and reliable noise calculation method and then correcting the error due to the discrepancy between the simulated coupling path and the coupling path of the actual device. This table is an excerpt from Patent Application No. 2017-077577 and shows that noise intensity can be accurately calculated from a signal that contains a mixture of noise and reproduced sound. However, this is the case when the noise and the reproduced sound are uncorrelated with each other. Generally, the driving noise and the reproduced sound are completely independent and uncorrelated. The parts related to this table and the present proposal are max(Noise), max(Sig), max(Noise+Sig), max(noise+Sig)-max(sig) Each vertical column represents the time around that time. Noise intensity, playback input signal intensity, signal intensity of noise and playback signal mixed, The value obtained by subtracting the noise intensity from the signal intensity of the noise and playback signal, This indicates that Let Y be the pure running vibration acceleration, and X be the signal mixed into the sensor detection signal through the coupling path from the playback signal to the vibration acceleration sensor, We show that PK(Y)=PK(X+Y)-PK(X) holds with high accuracy. That is, it is possible to accurately calculate the running vibration acceleration intensity. For example, if PK(Y) is 30 and PK(x) is 1.0, the value of Pk(X+Y)-PK(X) is 29.986, with an accuracy of 0.05%. This shows that in theory, it is possible to detect pure road noise with astonishing accuracy. In reality, an error of about 10% occurs due to the discrepancy between the simulated and actual coupled paths. This corresponds to a control amount of about 20 dB, but it is still an extremely effective method.

[0061] FIG. 7 is an explanatory diagram of the correction magnification based on the running vibration acceleration intensity. The horizontal axis represents the running vibration acceleration intensity, and the vertical axis represents the correction factor. Expansion Curve indicates that the figure is an example of expansion characteristics. RNL is the running vibration acceleration intensity, EXPgain is the compensation control signal, RNLstart is the minimum point of the input playback signal strength intonation correction. RNLmax is the maximum point of intonation correction of the input playback signal strength. EXPmax is the maximum correction factor. The slope range of the correction starts at RNLstart and goes up to RNLmax. The correction characteristic EXPgain corrects the intonation of the input playback signal strength, corrects the intonation of the clear component, This is the intermediate signal that is the basis for volume and sound quality correction. The specific numerical control characteristics are determined by design.

[0062] FIG. 8 is an explanatory diagram of sound quality and volume correction based on the intensity of running vibration acceleration. The essence of this invention is to correct the sound quality and volume in accordance with the corrected vibration acceleration intensity. The running vibration acceleration increases with the running speed. The low frequency components tend to rise when the vehicle speed is low, and the high frequency components tend to become stronger as the vehicle speed increases. Therefore, the optimal control for the listener in terms of the intensity corresponding to the vehicle noise is Varies depending on the playback frequency band. This diagram shows an example of control for three types of volume: bass, treble, and overall volume. The horizontal axis represents the running vibration, and the vertical axis represents the intensity correction factor. Compensation Curve indicates that the figure is an example of the characteristics of intensity compensation. Explanation of the same symbols as in FIG. 7 will be omitted. Gain Compensation is the amount of intensity compensation. 0dB is no correction, Sample 1, Sample 2, and Sample 3 are examples of overall intensity, bass intensity, and treble intensity correction, respectively. S1max, S2max, S3max are the maximum correction amounts for Sample1, Sample2, and Sample3, respectively. is. The specific numerical control characteristics are determined by design.

[0063] 9 is an explanatory diagram of the closed-loop gain margin of the control system for the playback signal strength based on the running vibration acceleration strength before and after improvement, where the horizontal axis represents the strength correction amount and the vertical axis represents the gain margin. The closed-loop gain margin of the signal strength control system is not as difficult as the control of a linear system, and The system will be stable if the error in the strength is corrected. However, if the error is corrected too much in the direction of stability, the accuracy will deteriorate, so the degree of error correction is determined by a trade-off between performance and stability. This shows that the overall control range after improvement by this proposal is significantly expanded whether the closed-loop gain margin is 3dB or 6dB. 43dB is the target value, and is a achievable figure. Gain Margin by Compensation is the gain margin by intensity compensation. Total Gain Compensation: Variation by RNL & Signal The horizontal axis is the total gain correction, i.e., the intensity correction amount, which depends on the RNL and the signal condition. Loop Gain Margin is the gain margin of the control system. 0dB, ​​3dB, 6dB are the closed-loop gain margins, Before Improved is the characteristic before improvement, After Improved indicates the characteristics after improvement. is. The essence of this invention is to significantly improve the overall control range by combining multiple elements.

[0064] FIG. 10 is a block diagram illustrating the basic design for realizing the present invention. It consists of a detection unit, a control signal generation unit, and a control unit. Sin is the input playback signal, Sout is the output of the sound quality generator and is the original playback signal.

[0065] Coupling Detection is responsible for calculating the strength of the component that is dependent on the original playback signal and is included in the detected vibration acceleration. The purpose is to cancel out the component strength of the original playback signal contained in the intensity of the detected vibration acceleration. Rather than subtracting linearly, it subtracts at the intensity level. Details are explained in Figure 6. Sreplay is the original playback signal, PseudoC() simulated connection path, Intensity in Pk() (), R is the error correction coefficient for the output strength of the simulated coupling path, R*PK(PseudoC(Sreplay)) is the output of Coupling Detection.

[0066] ACC Detection is a function that detects driving vibration acceleration. The purpose is to use the intensity of vibration acceleration as a substitute for running noise because running noise contains many reproduced sound components, while vibration acceleration contains few reproduced sound components. Furthermore, there is a strong linear correlation between running noise and vibration acceleration. Details are explained in Figure 4. The sensor element is usually mounted on a printed circuit board for convenient integration. The location of the sensor is determined by the design. Accin is the detection signal of the driving vibration acceleration, PK() is the strength in (), PK(ACCin) is the driving vibration acceleration intensity, Bias is a fixed amount of background or miscellaneous noise. If the bias does not affect performance, there is no need to provide it. Since PK(ACCin) includes the intensity of the vibration component generated by the speaker, The running vibration acceleration intensity RNL used to control the entire system is It is calculated by subtracting R*(PK(PSEUDOC(Sreplay)) and Bias from PK(ACCin). RNL = PK(ACCin)-R*(PK(PSEUDOC(Sreplay))-Bias). RNL is the corrected running vibration acceleration intensity.

[0067] Compensation Curve The corrected control signal EXPgain is generated from the corrected running vibration acceleration intensity RNL. This is a function for generating a correction curve. This curve is determined by design based on the relationship between noise and reproduced sound and auditory perception. In a proportional relationship, The volume is abnormally loud when driving at high speeds, and the ultra-low noise is surprisingly loud when driving at low speeds and with low noise levels, making it unsuitable for practical use. Details are explained in Figure 8. CMP is the correction polar generator.

[0068] EXPC is an intensity intonation correction function. The stronger the noise, the more inaudible the playback sound becomes in the weak range of the input playback signal with strong intonation. In particular, with announcements, the more frequently there are inaudible parts, the more likely it is that the entire announcement will become inaudible. Therefore, the intensity of the playback sound is maintained at a constant level in order to reduce the number of inaudible parts even in loud noise. Details are shown in Figure 2. EXPctrl generates the control signal Kexp under the control of the correction control signal EXPgain. EXP is controlled by Kexp to produce the intensity-corrected signal Sexp.

[0069] The SMDC is a calculation unit for the SM degree of the input playback signal, It consists of a control section for controlling the mixing ratio of announcement quality signals and music quality signals. Details are shown in Figure 1. SMD is a function to calculate the degree of SM SMDctrl controls the mix ratio of announcement quality signals and music quality signals

[0070] LEFC is a component that generates sound quality for music. Details are explained in Figure 12. LEF is the music quality generator LEFctrl controls the generation characteristics of the music signal generator in response to road noise, and Function to suppress saturation of the playback system Klef is the signal that LEFctrl controls the LEF. Slef is a musical quality signal

[0071] CLRC is a clear component intensity intonation correction function, the details of which are explained in Figure 3. CLRctrl receives EXPgain and controls the stabilization of the intonation of the clear component strength, and SOUTpk is controlled to avoid saturation of the regeneration system. Kclr is the control signal CLR generates the audio quality for announcements under the control of Kclr.

[0072] TVRC is an overall volume and sound quality correction function, details of which are explained in Figure 8. TVctrl receives EXPgain and controls the intensity of the original playback output signal Kcler is the control signal TVR is controlled by Kclr to control the intensity of the original playback signal.

[0073] FIG. 11 shows an example of statistical data of a signal required for detecting the degree of SM of an input reproduction signal and its application. In both cases, the data was actually measured by changing the mixing ratio of the intensity of the complete announcement signal and the complete music signal in order to verify objectivity. (a) shows the change in statistical properties when the mixing ratio of announcement signals and music signals is changed. (b) shows the change in statistical properties when the mixing ratio of announcement signals and natural environmental noise signals is changed. (c) shows the change in statistical properties when the mixing ratio of the announcement signal and the crisp guitar performance signal, which is statistically close to the speech signal, is changed. is. (a), (b), and (c) The vertical axis represents the amplitude of the input reproduced signal, and the horizontal axis represents the probability of occurrence of an amplitude smaller than the amplitude indicated on the vertical axis. The occurrence probability is the number of occurrences per unit time, counted up by one for each occurrence in each sampling period. The tendency of announcement signals is closer to impulse than music signals, Music signals tend to be more sinusoidal than announcement signals. This can be visually identified from the figures (a), (b), and (c). If it can be distinguished visually, it can also be distinguished by calculation. An example of a method for measuring the degree of SM is Patent Application No. 2018-093666. (d) is the output of the SM degree detection function, FIG. 10 is an explanatory diagram of the relationship between the mixing ratio of the outputs of the announcement filter and the music filter and the degree of SM. The SMD Curve shows the relationship between the SMD degree and the mixture ratio. The horizontal axis SMD is the degree of SM. SMDa is the SMD value of perfect announcement, and SMDm is the SMD value of perfect music. The characteristics of the mixture ratio corresponding to the degree of SM are determined by design. For example, it can be straight like SMD1 or curved like SMD2. The left vertical axis a0 to a100 indicates the mixing ratio of the announcement signal from 0% to 100%. The right vertical axis m0 to m100 indicates the mixing ratio of the music signal from 0% to 100%.

[0074] FIG. 12 is an explanatory diagram of the function of synthesizing the sound quality of a music signal. (a) is a block diagram. The relationship between the intensity of running noise and the mid-range sound is This function allows you to adjust bass and treble emphasis independently from the auditory sense. The boundary between the midrange and This is a filter configuration in which the physical characteristics of gain and phase characteristics are continuously connected. It also produces extremely good sound quality over a wide range. Furthermore, the control range of the characteristics is wide, the control is easy at high speed, there are no unstable factors, and the filter configuration is extremely easy to use for this invention. The transfer function shown in the block of the block diagram is a general first-order FIR filter, so a detailed explanation will be omitted. Let j be a complex operator and ω be the angular velocity, Tb is the time constant of the high-cut filter, 1 / (1+jωTb) is a first-order high-cut filter, Fbase is for bass and ultra-bass. The time constant Tb is determined by design. As an example, the time constant suitable for driving noise is 47Hz in terms of f0. Tt is the time constant of the low-cut filter, jωTb / (1+jωTb) is a first-order low-cut filter, Ftreble is for high and ultra-high frequencies. The time constant Tt is determined by design, As an example, the time constant suitable for driving noise is 12 kHz in terms of f0. Sexp is the input playback signal and Slef is the output. Kb is the bass amplification coefficient. The value is determined by design. For example, 30 dB Kt is the treble amplification coefficient, the value of which is determined by design, but an example is 24 dB. The bass signal and treble signal amplified by Kb Kt are added together, multiplied by Klef, and the sign is inverted. This signal is the Slef music playback signal. Klef is In order to prevent the output of the power amplifier from being saturated by the original playback signal Sout, which is the input of the power amplifier, the compensation control signal EXPgain is adjusted according to the intensity of the road noise. To be controlled. Expressed in a formula, Let Kb * (1 / (1+jωTb)^2)) * Sexp be the bass maximum emphasis signal Fbase(Sexp), Let Kt * ((jωTt) / ((1+jωTt)^2) * Sexp be the treble emphasis signal Ftreble(Sexp), Kb * (1 / (1+jωTb)^2) + Kt * ((jωTt) / ((1+jωTt)^2) is the maximum emphasis signal for sound quality. The coefficient Klef is controlled by LEFctrl and changes depending on the state of the system. LEFctrl is the EXPgain that depends on the driving noise, It is determined by SOUTpk=Qh / S(PK(Sout)), which depends on the original output signal Sout, The decision procedure is as follows: As the road noise gets stronger, Klef becomes larger, and Sout acts to reduce Klef so that the maximum strength of the regenerative system does not become saturated. The specific calculation formula for Klef shall be determined by design. Musical quality signals are Sexp = Sexp - (Fbase(Sexp) + Ftreble(Sexp)) * Klef This becomes:

[0075] (b) is an example of the frequency gain characteristics of the sound quality generated by the block diagram (a); Controlled by Klef, the characteristics change from LEF1 to LEF6. The characteristics of LEF1 are such that bass and treble are most emphasized depending on the input playback signal condition, the playback volume selected by the user, and the road noise condition. The characteristics of LEF6, on the other hand, are closest to the least emphasized state. The characteristics are based on the condition that the output of the power amplifier does not exceed the maximum limit output. Automatically adjusts to the optimum condition.

[0076] The following is a supplementary explanation of each claim. Supplementary explanation of claim 1 (including excerpts from claim 1) The following is an excerpt from claim 1. The input reproduction signal is the input reproduction signal for the signal processing of the present invention, The output reproduction signal is the output of the reproduction signal of the signal processing of the present invention, An announcement signal is an audio signal that can be recognized by humans as information when the input playback signal is played back. Specific examples include announcement signals such as news, weather forecasts, and stock price information. A music signal is a signal that can be recognized by humans as music with instruments or vocals when the input playback signal is played back, as well as other signals that include natural environmental noise. The original playback signal is a signal that is combined with the speaker drive signal at a fixed constant. The original playback signal in the actual device is input to the power amplifier, The intensity is the maximum value of the signal within a certain period of time. A function is a set of electronic elements, circuits, algorithms, and programs that perform a specific function. Either way, The driving vibration acceleration signal is a signal obtained by amplifying the output of an acceleration sensor attached to a structure connected to the vehicle body. The intensity of the running vibration acceleration signal is defined as the running vibration acceleration intensity. Strong noise is defined as a noise of 90 dB or more, which can be heard from the driver's seat when a standard passenger car is traveling at around the speed limit on a highway with poor road conditions. The intensity of the vehicle's running noise is defined as the running noise intensity. First, we take advantage of the fact that the actual measurement results show a strong linear correlation between the running vibration acceleration intensity and the running noise intensity. The car audio playback device is used as the playback device. The coupling path is the vibration path from the original playback signal of the playback device, through the vibration generated by the speaker, and then through the structure and air to the acceleration sensor. Secondly, we take advantage of the fact that the strength of the coupling path using an acceleration sensor is significantly smaller than when using a microphone for detecting sound waves. This significantly small difference is due to a difference of 13 dB in the actual measurement value of an example of a popular car. A function that simulates a coupling path is defined as a simulated coupling path, The intensity of the output signal of the simulated coupling path is set as the simulated coupling signal intensity, The coefficient multiplied by the simulated combined signal strength is set as an error correction coefficient, The error correction coefficient is greater than 1. The simulated coupling signal strength is multiplied by the error correction coefficient to obtain the corrected simulated coupling strength. The simulated coupling strength after correction may have errors due to differences in the characteristics of the simulated coupling path and the actual coupling path. The property that the probability that the operation of the control system will enter the unstable range is affected is utilized. This can be achieved by adjusting the error correction coefficients: By weighing the sacrifice of the accuracy of the control system against the stability of the control system, it is possible to achieve both the required accuracy and the required stability to a satisfactory state in light of practicality. Third, the use of an error correction coefficient; This "reaching a satisfactory state" means that it is possible to determine that an improvement of 30 dB is possible between the theoretical value and the actual measured value. The value obtained by linearly subtracting the corrected simulated bond strength from the running vibration acceleration strength is The corrected running vibration acceleration intensity is The fourth feature is to have a function of controlling the degree of inflection of the intensity of the input playback signal of the playback device depending on the degree of the corrected running vibration acceleration intensity; The fifth feature is to have a function of controlling the volume and sound quality of the input playback signal of the playback device depending on the degree of the corrected driving vibration acceleration intensity; The sixth requirement is that the input playback signal has a function to detect the degree of SM, i.e., whether it is announcement-oriented or musical-oriented. What is SM degree? Based on the amplitude distribution of the input playback signal within a unit time, Input playback signal Including the intermediate range from perfect announcement to perfect musicality. The degree of this is expressed as a numerical value, The unit time is, for example, a time interval of approximately 1 to 8 seconds, and the measurement time width is It shall be determined by design. Depending on the SM degree value, The seventh requirement is that the device has a function for controlling the mixing ratio between the output of a filter suitable for announcement playback and the output of a filter suitable for music playback. The first, second, third, fourth, fifth, sixth, and seventh signals are included to obtain an output reproduction signal. A method for controlling sound quality and volume of a car playback device. The above is an excerpt from claim 1.

[0077] The following is a supplementary explanation of claim 1. Regarding loud noise, It is common knowledge that when expressing noise numerically, the numbers vary greatly depending on whether or not auditory weighting is applied. In particular, when it comes to vehicle noise, the bass components are strong, and the numerical value varies greatly depending on the vehicle type and road surface conditions. The 90 dB in claim 1 is a C-weighted numerical value. Generally, noise is often evaluated using A-weighted noise, but when listening to music on car audio, the reproduced sound in the ultra-low frequency range is one of the important evaluations, so the C-weighted numerical value, which has a small correction for the weight of the bass, is used. The actual measurement results of driving noise on a bad road surface on a highway are as follows: For a slightly larger passenger car with good driving noise control, the noise level is 90dB to 100dB. For small, popular EVs, the noise level is 96dB to 106dB. In the light vehicle class, it reaches 100dB to 110dB. This is just an example of actual measurement results, and does not represent actual measurement results for all road surfaces and tire conditions. The numerical values ​​in the claim are considered to be noise that interferes with conversation with the passenger in the passenger seat, and that makes it difficult to hear the details of broadcasts containing numerical information unless the volume is turned up higher than normal. The C characteristic is 90dB. FIG. 10 is a block diagram of a specific example of claim 1. The supplementary explanation is the same as that for FIG. 10, so it will be omitted. The above is a supplementary explanation of claim 1.

[0078] Supplementary explanation of claim 2 (including excerpts from claim 2) The following is an excerpt from claim 2. The clarity of the input playback signal of the playback device is determined depending on the degree of the corrected running vibration acceleration intensity. The eighth point is that it has the function of stabilizing intonation. The inflection of clarity refers to the inflection of the intensity of the clarity component, which is constantly changing, separate from the signal intensity. The eighth aspect of the present invention is characterized by having the first, second, third, fourth, fifth, sixth and seventh aspects of claim 1; Depend on the corrected control signal which depends on the corrected driving vibration acceleration intensity, It has a control function to stabilize the intonation of clarity. A method for controlling the sound quality volume of a car playback device. The above is an excerpt from claim 2. The above is a supplementary explanation of claim 2.

[0079] Supplementary explanation of claim 3 (including an excerpt from claim 3) The following is an excerpt from claim 3. Regarding the sound quality filter suitable for reproducing music in a road noise environment as described in claim 1, The signal is amplified by the output of a filter that has two first-order high-cut filters connected in series. a signal that emphasizes the bass quality of the music signal, and this signal is called a bass emphasis signal; The signal is amplified by the output of a filter that has two first-order low-cut filters connected in series. a signal that emphasizes the quality of high frequencies in the music signal, and this signal is called a treble emphasis signal; A signal obtained by adding the bass emphasis signal and the treble emphasis signal is used as a music sound quality emphasis signal, The means for generating the music quality enhancement signal is a music quality generation function, For music quality enhancement signals, Corrected control signal that depends on the corrected running vibration acceleration intensity and The sound quality optimization function is a means of multiplying a dynamically changing coefficient by applying a signal corresponding to the strength of the original playback signal to satisfy both sound quality corresponding to road noise and sound quality corresponding to preventing saturation of the playback system. The ninth point is that it has a music sound quality generation function and a sound quality optimization function. 9. The invention is characterized by comprising the first, second, third, fourth, fifth, sixth and seventh features of claim 1. However, there is a method for controlling the sound quality and volume of a car playback device having a function for controlling the sound quality of music. The above is an excerpt from claim 3.

[0080] The following is a supplementary explanation of claim 3. FIG. 12 is a block diagram and an explanatory diagram of a specific example of claim 3. The supplementary explanation is the same as that for FIG. 12, so it will be omitted. In a wide range of noise levels from weak to strong, The sound quality is well balanced between low and high frequency noise, You can set the sound quality of the bass and treble independently, Stable high-speed control, It can reproduce a sound quality with a sense of contrast in relation to the mid-range. The above is a supplementary explanation of claim 3.

[0081] Supplementary explanation of claim 4 (including an excerpt from claim 4) The following is an excerpt from claim 4. PK() is the strength of the signal in (), Let Q / Q be the time constant for fast attack and fast release. Let Qh / S be the fast attack time constant, maximum hold time, and slow release time constant. The time constants and hold times are determined by design. The corrected running vibration acceleration intensity of claim 1 is set to a range from a minimum point RLNstart to a maximum point RNLmax, Generate a correction control signal EXPgain with a slope corresponding to RNLstart to RNLmax, EXPgain is used to compensate for the intensity inflection of the input playback signal; The intensity of the input playback signal is defined as input playback signal intensity PK(Sin), PK(Sin) is the common input for two time constant functions Q / Q and Qh / S with different time constants, The difference between the outputs of Q / Q and Qh / S, which occurs due to the time difference between their releases, is used. The signal obtained by subtracting the output of the Q / Q side from the output of the Qh / S side is Generate the signal Qh / S((PK(Sin))-Q / Q(PK(Sin)) that is the basis of the expansion control signal, The correction control signal Expgain is applied, The function to obtain a signal by normalizing Qh / S((PK(Sin))-Q / Q(PK(Sin)) with Qh / S((PK(Sin)) is called the expansion control signal generation function Expctrl. The output of Expctrl is the expansion control signal Kexp, Kexp is the input of the intensity intonation correction function EXP, The tenth point is to correct the inflection of the input playback signal strength corresponding to the corrected running vibration acceleration using Kexp; The fourth clause of claim 1 replaces the tenth clause; The tenth aspect and the first, second, third, fifth, sixth and seventh aspects of claim 1 are included. However, there is a method for controlling the sound quality and volume of a car playback device having a function for controlling the sound quality of music. The above is an excerpt from claim 4. The following is a supplementary explanation of claim 4. FIG. 2 is an explanatory diagram of a specific example of claim 4. The supplementary explanation is the same as that for FIG. 2, so it will be omitted. In particular, announcement signals have large fluctuations in signal strength. The stronger the noise level, the greater the chance of not being able to hear weaker parts of the signal. This makes it difficult to hear the information. To address this issue, the strength of short-term intonation in the signal is corrected. The above is a supplementary explanation of claim 4.

Claims

1. The input reproduction signal is the input reproduction signal for the signal processing of the present invention, The output reproduction signal is the output of the reproduction signal of the signal processing of the present invention, An announcement signal is an audio signal that can be recognized by humans as information when the input playback signal is played back. Specific examples include announcement signals such as news, weather forecasts, and stock price information. A music signal is a signal that can be recognized by humans as music with instruments or vocals when the input playback signal is played back, as well as other signals that include natural environmental noise. The original playback signal is a signal that is combined with the speaker drive signal at a fixed constant. The original playback signal in the actual device is input to the power amplifier, The intensity is the maximum value of the signal within a certain period of time. A function is a set of electronic elements, circuits, algorithms, and programs that perform a specific function. Either way, The driving vibration acceleration signal is a signal obtained by amplifying the output of an acceleration sensor attached to a structure connected to the vehicle body. The intensity of the running vibration acceleration signal is defined as the running vibration acceleration intensity. Strong noise is defined as a noise of 90 dB or more, which can be heard from the driver's seat when a standard passenger car is traveling at around the speed limit on a highway with poor road conditions. The intensity of the vehicle's running noise is defined as the running noise intensity. First, we take advantage of the fact that the actual measurement results show that there is a strong linear correlation between the running vibration acceleration intensity and the running noise intensity. The car audio playback device is used as the playback device. The coupling path is the vibration path from the original playback signal of the playback device, through the vibration generated by the speaker, and then through the structure and air to the acceleration sensor. Secondly, we take advantage of the fact that the strength of the coupling path using the acceleration sensor is significantly smaller than when using a microphone for detecting sound waves. This significantly small difference is due to a difference of 13 dB in the actual measurement value of an example of a popular car. A function that simulates a coupling path is defined as a simulated coupling path, The intensity of the output signal of the simulated coupling path is set as the simulated coupling signal intensity, The coefficient multiplied by the simulated combined signal strength is set as an error correction coefficient, The error correction coefficient is greater than 1, The simulated coupling signal strength is multiplied by the error correction coefficient to obtain the corrected simulated coupling strength. The simulated coupling strength after correction may have errors due to differences in the characteristics of the simulated coupling path and the actual coupling path. The property that the probability that the operation of the control system will enter the unstable range is affected is utilized. This can be achieved by adjusting the error correction coefficients: By weighing the sacrifice of the accuracy of the control system against the stability of the control system, it is possible to achieve both the required accuracy and the required stability to a satisfactory state in light of practicality. Third, using an error correction factor; This "reaching a satisfactory state" means that it is possible to determine that an improvement of 30 dB is possible between the theoretical value and the actual measured value. The value obtained by linearly subtracting the corrected simulated bond strength from the running vibration acceleration strength is The corrected running vibration acceleration intensity is Fourth, the device has a function of controlling the degree of inflection of the intensity of the input reproduction signal to the reproduction device depending on the degree of the corrected running vibration acceleration intensity; The fifth feature is to have a function of controlling the volume and sound quality of the input playback signal of the playback device depending on the degree of the corrected running vibration acceleration intensity. The sixth requirement is that the input playback signal has a function to detect the degree of SM, i.e., whether it is announcement-oriented or musical-oriented. What is SM degree? Based on the amplitude distribution of the input playback signal within a unit time, Including the mid-range from perfect annunciation to perfect musicality of the input playback signal. The degree of this is expressed as a numerical value, The unit time is, for example, a time interval of approximately 1 second to 8 seconds, and the measurement time width is It shall be determined by design. Depending on the value of SM degree, The seventh feature is that the device has a function for controlling the mixing ratio between the output of a filter suitable for announcement playback and the output of a filter suitable for music playback. The present invention is characterized in that it has first, second, third, fourth, fifth, sixth and seventh components and obtains an output reproduction signal. A method for controlling the sound quality volume of a car playback device.

2. The clarity of the input playback signal of the playback device is determined depending on the degree of the corrected running vibration acceleration intensity. The eighth point is that it has the function of stabilizing intonation. The intonation of clarity is not general clarity, The intensity of the clear component changes constantly, separate from the signal intensity. The eighth aspect and the first, second, third, fourth, fifth, sixth and seventh aspects of claim 1 are included, Depend on the corrected control signal which depends on the corrected driving vibration acceleration intensity, It has a control function to stabilize the intonation of clarity. A method for controlling the sound quality volume of a car playback device.

3. A sound quality filter suitable for reproducing music in a noisy environment as described in claim 1, The signal is amplified by the output of a filter that has two first-order high-cut filters connected in series. a signal that emphasizes the bass quality of the music signal, and this signal is called a bass emphasis signal; The signal is amplified by the output of a filter that has two first-order low-cut filters connected in series. a signal that emphasizes the quality of high frequencies in the music signal, and this signal is called a treble emphasis signal; A signal obtained by adding the bass emphasis signal and the treble emphasis signal is used as a music sound quality emphasis signal, The means for generating the music quality enhancement signal is a music quality generation function, For music quality enhancement signals, Corrected control signal that depends on the corrected running vibration acceleration intensity and The sound quality optimization function is a means of multiplying a dynamically changing coefficient by applying a signal corresponding to the strength of the original playback signal to satisfy both sound quality corresponding to road noise and sound quality corresponding to preventing saturation of the playback system. The ninth point is that it has a music sound quality generation function and a sound quality optimization function. The ninth aspect and the first, second, third, fourth, fifth, sixth and seventh aspects of claim 1 are included. However, there is a method for controlling the sound quality and volume of a car playback device having a function for controlling the sound quality of music.

4. PK() is the strength of the signal in (), Let Q / Q be the time constant for fast attack and fast release. Let Qh / S be the fast attack time constant, maximum hold time, and slow release time constant. The time constants and hold times are determined by design. The corrected running vibration acceleration intensity of claim 1 is set to have a range from a minimum point RLNstart to a maximum point RNLmax, Generate a correction control signal EXPgain with a slope corresponding to RNLstart to RNLmax, EXPgain is used to compensate for the intensity inflection of the input playback signal; The intensity of the input playback signal is defined as input playback signal intensity PK(Sin), PK(Sin) is the common input for two time constant functions Q / Q and Qh / S with different time constants, The difference between the outputs of Q / Q and Qh / S, which occurs due to the time difference between their releases, is used. The signal obtained by subtracting the output of the Q / Q side from the output of the Qh / S side is Generate the signal Qh / S((PK(Sin))-Q / Q(PK(Sin)) that is the basis of the expansion control signal, The correction control signal Expgain is applied, The function to obtain a signal by normalizing Qh / S((PK(Sin))-Q / Q(PK(Sin)) with Qh / S((PK(Sin)) is called the expansion control signal generation function Expctrl. The output of Expctrl is the expansion control signal Kexp, Kexp is the input of the intensity intonation correction function EXP, The tenth point is to correct the inflection of the input reproduction signal intensity corresponding to the corrected running vibration acceleration using Kexp; The fourth clause of claim 1 is replaced by the tenth clause; The tenth aspect and the first, second, third, fifth, sixth and seventh aspects of claim 1 are included. However, there is a method for controlling the sound quality and volume of a car playback device having a function for controlling the sound quality of music.

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