Signal processing device, signal processing method, and signal processing system

Abstract

To provide a signal processing device capable of performing loudness correction of audio signals as designed.SOLUTION: A signal processing device includes a first correction unit (tone control, AVCEQ) and a second correction unit (dynamic loudness compensation). The first correction unit corrects the frequency characteristics on the input audio signal according to the settings made by the user and the state of the vehicle in which the audio signal is reproduced. The second correction unit performs loudness correction according to the characteristics of the audio signal on the audio signal corrected by the first correction unit.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to a signal processing device, a signal processing method, and a signal processing system. [Background technology]

[0002] Conventionally, audio systems installed in vehicles are equipped with a loudness correction function (see, for example, Patent Document 1), an automatic volume adjustment function (AVC: Automatic Volume Control), and a tone control function as functions for correcting the playback frequency characteristics.

[0003] The loudness correction function compensates for the human hearing characteristic that makes it difficult to hear low and high sounds when the playback volume is low, by adjusting the frequency characteristics to increase low and high sounds when the playback volume is low.

[0004] Here, the loudness correction function according to the volume control by the user is called a static loudness correction function, and the loudness correction function according to the characteristics of the audio signal is called a dynamic loudness correction function.

[0005] In addition, AVC is provided to avoid the masking phenomenon caused by driving noise during music playback, and is a function that adjusts the volume and frequency characteristics of the playback sound according to the vehicle conditions such as driving speed.

[0006] The tone control function allows the user to adjust the frequency characteristics to suit his or her preferences. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] JP 2009-111538 A Summary of the Invention [Problem to be solved by the invention]

[0008] However, the conventional techniques have a problem in that loudness correction for an audio signal may not be performed as intended by design.

[0009] Fig. 10 is a diagram showing a conventional signal processing device. As shown in Fig. 10, (4) tone control (user-variable frequency characteristic correction unit 102a) and (5) AVCEQ (masking avoidance unit 103a) are arranged in the subsequent stage (output side) of (2) dynamic loudness compensation.

[0010] Here, the dynamic loudness correction function performs nonlinear processing, which results in harmonic components in the audio signal processed by the dynamic loudness correction function.

[0011] Fig. 11 is a diagram for explaining a problem with a conventional signal processing device. As shown in Fig. 11, there may be an area where the control bands of (4) tone control and (2) dynamic loudness compensation overlap.

[0012] In that case, the harmonic components that arise in the design of the loudness correction function will be emphasized by the tone control function.

[0013] Here, the tone control and AVC are adjusted based on user settings and external factors such as vehicle speed, while the dynamic loudness correction function adjusts according to design intent.

[0014] Therefore, when harmonic components are emphasized by the loudness correction function, the output audio signal may deviate from what was intended in the design.

[0015] The present invention has been made in view of the above, and has an object to provide a signal processing device, a signal processing method, and a signal processing system that are capable of performing loudness correction on an audio signal as intended by design. [Means for solving the problem]

[0016] In order to solve the above problems and achieve the object, the signal processing device according to the present invention has a first correction unit and a second correction unit. The first correction unit corrects the frequency characteristics of an input audio signal according to the contents of a user's settings and the state of a vehicle in which the audio signal is reproduced. The second correction unit corrects loudness of the audio signal corrected by the first correction unit according to the characteristics of the audio signal. Effect of the Invention

[0017] According to the present invention, loudness correction for an audio signal can be performed as intended by design. [Brief description of the drawings]

[0018] [Figure 1] FIG. 1 is a functional block diagram showing an example of the configuration of a signal processing device according to the first embodiment. [Diagram 2] FIG. 2 is a diagram showing a detailed configuration of the signal processing device according to the first embodiment. [Diagram 3] FIG. 3 is a diagram for explaining linear processing and nonlinear processing. [Figure 4] FIG. 4 is a diagram illustrating the effects of the first embodiment. [Diagram 5] FIG. 5 is a flowchart showing a procedure of processing executed by the signal processing device according to the first embodiment. [Figure 6] FIG. 6 is a diagram showing a detailed configuration of the signal processing device according to the second embodiment. [Figure 7] FIG. 7 is a diagram showing a detailed configuration of a signal processing device according to the third embodiment. [Figure 8] FIG. 8 is a diagram showing a process flow for calculating the correction amount. [Figure 9] FIG. 9 is a diagram for explaining the arbitration process of the correction amount. [Figure 10] FIG. 10 is a diagram showing a conventional signal processing device. [Figure 11]FIG. 11 is a diagram for explaining a problem with the conventional signal processing device. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0019] Hereinafter, embodiments of a signal processing device, a signal processing method, and a signal processing system disclosed in the present application will be described in detail with reference to the accompanying drawings. Note that the present invention is not limited to the embodiments described below.

[0020] [First embodiment] The configuration of a signal processing device according to the first embodiment will be described with reference to Fig. 1. Fig. 1 is a functional block diagram showing an example of the configuration of a signal processing device according to the first embodiment.

[0021] The signal processing device 1 is assumed to be mounted on a vehicle. The signal processing device 1 receives an input of an audio signal. The signal processing device 1 also outputs a processed audio signal.

[0022] Furthermore, the signal processing device 1 receives inputs of user operation information, vehicle speed information, and the like.

[0023] For example, the audio signal may relate to music to be reproduced in a vehicle. In this case, the signal processing device 1 processes the input audio signal to improve the reproduction quality of the music.

[0024] For example, the signal processing device 1 performs AVC, tone control, dynamic loudness compensation, and static loudness compensation on an audio signal.

[0025] Here, as shown in FIG. 10, in the conventional signal processing device, tone control and AVC are performed after dynamic loudness compensation is performed.

[0026] For this reason, as described above, there has conventionally been a problem in that loudness correction of an audio signal cannot be performed as intended by design.

[0027] On the other hand, the signal processing device of the first embodiment avoids the problem that loudness correction cannot be performed as intended by performing tone control and AVC before dynamic loudness compensation.

[0028] As shown in FIG. 1, the signal processing device 1 has a volume adjustment unit 101, a user-variable frequency characteristic correction unit 102, a masking avoidance unit 103, a playback volume level detection unit 104, a dynamic loudness correction amount calculation unit 105, a dynamic loudness correction unit 106, a static loudness correction unit 107, and a frequency characteristic correction unit 108.

[0029] Furthermore, the signal processing device 1 includes a volume gain calculation unit 201 , a user variable frequency correction amount calculation unit 202 , a masking avoidance correction amount calculation unit 203 , and a static loudness correction amount calculation unit 204 .

[0030] The volume gain calculation unit 201 calculates the adjustment amount of the playback volume to be performed by the volume adjustment unit 101 based on the user's operation information.

[0031] The volume adjustment unit 101 adjusts the playback volume based on the calculation result of the volume gain calculation unit 201 .

[0032] The user variable frequency correction amount calculation unit 202 calculates the amount of adjustment of the frequency characteristics in the tone control based on the user's operation information.

[0033] The user variable frequency characteristic correction unit 102 performs tone control based on the calculation result by the user variable frequency correction amount calculation unit 202 .

[0034] The masking avoidance correction amount calculation unit 203 calculates the amount of adjustment of the frequency characteristic in AVC based on the user's operation information and the vehicle speed information. The masking avoidance unit 103 performs AVC based on the calculation result by the masking avoidance correction amount calculation unit 203.

[0035] The playback volume level detection unit 104 detects the level of the playback volume after adjustment by the volume adjustment unit 101 .

[0036] The dynamic loudness correction amount calculation unit 105 calculates the amount of correction for a predetermined frequency band in dynamic loudness compensation based on the detection result of the playback volume level detection unit 104 .

[0037] The dynamic loudness correction unit 106 performs dynamic loudness compensation based on the calculation result by the dynamic loudness correction amount calculation unit 105 .

[0038] The static loudness correction amount calculation unit 204 calculates the correction amount for a predetermined frequency band in static loudness compensation based on user operation information (for example, the adjustment amount of the playback volume).

[0039] The static loudness correction unit 107 performs static loudness compensation based on the calculation result by the static loudness correction amount calculation unit 204 .

[0040] The frequency characteristic correction unit 108 performs other processes for correcting the frequency characteristics, except that the frequency characteristic correction unit 108 performs processes that are not based on user operation information.

[0041] Fig. 2 is a diagram showing a detailed configuration of the signal processing device according to the first embodiment. For the sake of explanation, Fig. 2 shows only main processing units extracted from the processing units described in Fig. 1.

[0042] First, (1) volume adjustment unit 101 is a function for adjusting the volume.

[0043] (4) The user variable frequency characteristic correction unit 102 performs tone control.

[0044] (2) Dynamic loudness compensation is performed by a playback volume level detection unit 104, a dynamic loudness correction amount calculation unit 105, and a dynamic loudness correction unit .

[0045] (3) Static loudness compensation is performed by the static loudness correction unit 107 and a static loudness correction amount calculation unit 204 provided in the host microcomputer.

[0046] Dynamic loudness compensation and static loudness compensation are processes for correcting predetermined high-frequency and low-frequency components.

[0047] At this time, in dynamic loudness compensation, the amount of compensation is determined according to the detected level of the playback volume, whereas in static loudness compensation, the amount of compensation is determined according to the set volume value.

[0048] Furthermore, dynamic loudness compensation involves linear processing, whereas static loudness compensation involves non-linear processing.

[0049] Fig. 3 is a diagram for explaining linear processing and nonlinear processing. As shown in Fig. 3, the relationship between the input signal level and the output signal level in linear processing is linear, just like before processing. On the other hand, the relationship between the input signal level and the output signal level in nonlinear processing is different from before processing.

[0050] Furthermore, in nonlinear processing (dynamic loudness compensation), by providing a smoothing gain to the correction amount, it is possible to make changes in the audio signal during a transition period natural and smooth.

[0051] Here, in the first embodiment, the user variable frequency correction amount calculation unit 202 and the masking avoidance correction amount calculation unit 203 correspond to a first correction unit.

[0052] That is, the user variable frequency correction amount calculation unit 202 and the masking avoidance correction amount calculation unit 203 correct the frequency characteristics of the input audio signal in accordance with the contents of the user settings and the state of the vehicle in which the audio signal is reproduced.

[0053] Furthermore, the dynamic loudness correction unit 106 performs loudness correction according to the level of the audio signal after the volume has been adjusted.

[0054] In the first embodiment, the dynamic loudness correction unit 106 and the static loudness correction unit 107 correspond to a second correction unit.

[0055] That is, the dynamic loudness correction unit 106 performs loudness correction on the audio signal corrected by the user variable frequency correction amount calculation unit 202 and the masking avoidance correction amount calculation unit 203 in accordance with the characteristics of the audio signal.

[0056] The characteristics of the audio signal are information available from the audio signal itself, e.g., the detected level, regardless of user action and vehicle state.

[0057] On the other hand, the static loudness correction unit 107 performs loudness correction by linear processing on the audio signal corrected by non-linear processing.

[0058] In this way, by arranging the processing whose results change depending on the user's operation and the vehicle state at a stage preceding (on the input side of) the dynamic loudness compensation, loudness correction can be performed as intended by design.

[0059] In particular, according to the first embodiment, it is possible to prevent harmonic components generated by dynamic loudness compensation from being emphasized by tone control and AVC.

[0060] Fig. 4 is a diagram for explaining the effect of the first embodiment. As shown in Fig. 4, in the first embodiment, even if the control bands of the tone control and the dynamic loudness compensation overlap, the harmonic components due to the dynamic loudness compensation are not emphasized by the tone control.

[0061] FIG. 5 is a flowchart showing a procedure of processing executed by the signal processing device according to the first embodiment.

[0062] 5, the signal processing device 1 receives an input of an audio signal (step S101). For example, the signal processing device 1 receives an input of an audio signal stored as an audio file in a storage device provided in a vehicle.

[0063] Next, the signal processing device 1 performs tone control on the audio signal (step S102).

[0064] Next, the signal processing device 1 performs AVC on the audio signal to avoid the masking phenomenon (step S103).

[0065] After that, the signal processing device 1 performs dynamic loudness compensation on the audio signal (step S104).

[0066] Then, the signal processing device 1 performs static loudness compensation on the audio signal (step S105).

[0067] Here, the signal processing device 1 outputs the processed audio signal (step S106). For example, the signal processing device 1 outputs the audio signal to a speaker of a vehicle.

[0068] Moreover, the signal processing device 1 can form a signal processing system together with a vehicle.

[0069] In this case, the vehicle has a storage unit that stores the audio signal before processing, and an output unit that converts the audio signal processed by the signal processing device 1 into sound and outputs it.

[0070] The signal processing device 1 receives an input of an audio signal stored in a storage unit, and outputs a processed audio signal to an output unit.

[0071] The storage unit may be realized by a storage medium such as an optical medium, a flash memory, etc. Furthermore, the storage unit may be a storage area of ​​a mobile terminal connected to the vehicle so as to be able to communicate data with the vehicle, or a server connected to the vehicle via a network.

[0072] Also, for example, the output unit is a speaker.

[0073] [Second embodiment] In the second embodiment, the signal processing device 1 performs noise-sensitive dynamic noise compensation in addition to the processing described in the first embodiment.

[0074] Fig. 6 is a diagram showing a detailed configuration of a signal processing device according to the second embodiment. As shown in Fig. 6, a dynamic noise compensation unit 304 is disposed after (on the output side of) the dynamic loudness correction unit 106.

[0075] The dynamic noise compensation unit 304 performs volume compensation for the part masked by noise on the audio signal corrected by dynamic loudness compensation based on the level calculation result (noise volume) of the noise signal collected by a microphone installed in the vehicle.

[0076] This eliminates the need for the user to change the volume value each time in response to noise such as road noise.

[0077] A vehicle speed-linked static noise compensation function such as AVC is known to prevent the reproduced sound from being difficult to hear inside the vehicle due to driving noise.

[0078] On the other hand, the running noise varies greatly not only depending on the vehicle speed but also on the location and conditions of the vehicle. For this reason, in the second embodiment, a sensor that monitors the running noise is added, and dynamic noise compensation is performed based on noise monitor information obtained from the sensor information.

[0079] In the example of Figure 6, both vehicle speed and microphone input are used to calculate the noise level. Vehicle speed is information that is highly correlated with driving noise. The microphone is a means for sensing noise.

[0080] Here, the masking avoidance unit 103 (AVCEQ) corresponds to static noise compensation that reduces noise based on vehicle speed information and a volume value.

[0081] As shown in FIG. 6, the masking avoidance unit 103 calculates the amount of correction by referring to Volume Tables corresponding to the adjustment amount of the playback volume by the volume adjustment unit 101 and AVC Tables corresponding to the vehicle speed pulse.

[0082] On the other hand, dynamic noise compensation is performed based on the results of analyzing noise inside the vehicle that is actually recorded with a microphone.

[0083] Specifically, the dynamic noise compensation correction amount calculation unit 303 calculates the correction amount based on the result of the reproduction sound component removal unit 301 removing the reproduction sound component by E / C processing from the noise signal input by the microphone.

[0084] Furthermore, the dynamic noise compensation correction amount calculation unit 303 may correct the audio signal obtained by removing the reproduced sound component from the audio collected by the microphone, using the components for each band obtained by filtering.

[0085] This allows for precise equalizer control for each frequency band.

[0086] The method of calculating the noise level is not limited to using the voice recorded by the microphone. The dynamic noise compensation correction amount calculation unit 303 may calculate the noise level based on information obtained from either or both of a vehicle signal that has a strong correlation with the running noise and the sensing result by the actuator.

[0087] Vehicle signals that are highly correlated with running noise include vehicle speed, engine speed, torque, etc. The actuator may be a microphone or a vibration sensor.

[0088] Furthermore, the signal processing device 12 may utilize actuators that are installed for other purposes, such as a microphone for hands-free calling and a sensor for ANC (Active Noise Control).

[0089] In order to detect only the actual noise volume from the signal input from the actuator, the signal processing device 12 convolves a transfer function with the audio signal to be reproduced and predicts the audio signal component to be input to the actuator.

[0090] The signal processor 12 then subtracts the predicted audio signal component from the input signal.

[0091] When a microphone is used as an actuator as in FIG. 6, the signal processing device 12 obtains and applies the transfer characteristics in the reproduction space (inside the vehicle) from the speaker output to the microphone input.

[0092] Furthermore, when a vibration sensor is used as the actuator, the signal processing device 12 obtains and applies the vehicle body propagation characteristics from the speaker to the vibration sensor.

[0093] Furthermore, a band limiting filter for the purpose of reducing the tap length of the FIR (Finite Impulse Response) filter used in the transfer function convolution in FIG. 6 may be provided in the preceding stage.

[0094] Furthermore, in order to improve the accuracy of detecting the amount of noise, a filter similar to the above-mentioned band-limiting filter may be inserted on the noise signal side (microphone input side) to eliminate the relative phase difference.

[0095] Furthermore, the microphone input can be filtered according to frequency or time characteristics, and the control content adjusted according to the respective detection results, thereby increasing sensitivity to specific noise types.

[0096] [Third embodiment] In the third embodiment, the signal processing device performs processing that integrates dynamic loudness compensation and dynamic noise compensation.

[0097] This is because the processing contents of dynamic loudness compensation and dynamic noise compensation are similar and both function as equalizers. This makes it possible to prevent a reduction in the effects of dynamic loudness compensation and dynamic noise compensation due to competition, and reduce the processing load.

[0098] Moreover, in the third embodiment, the signal processing device performs processing that integrates static loudness compensation, tone control, and AVC.

[0099] FIG. 7 is a diagram showing a detailed configuration of a signal processing device according to the third embodiment.

[0100] As shown in FIG. 7, the signal processing device 13 executes static loudness compensation, tone control and AVC in the front-stage part (static sound control integrated block: user variable frequency correction amount calculation unit 202, masking avoidance correction amount calculation unit 203, static loudness correction amount calculation unit 204, static control correction amount arbitration unit 401, static control correction unit 402).

[0101] In addition, the signal processing device 13 executes dynamic loudness compensation and dynamic noise compensation in the subsequent stages (dynamic sound control integrated block: dynamic loudness correction amount calculation unit 105, reproduced sound component removal unit 301, noise level detection unit 302, dynamic noise compensation correction amount calculation unit 303, dynamic control correction amount arbitration unit 403, static control correction unit 402).

[0102] In other words, the static audio control integrated block performs frequency characteristic correction on the input audio signal in accordance with the user settings and the state of the vehicle in which the audio signal is being played, as well as loudness correction using linear processing.

[0103] In addition, the dynamic sound control integrated block determines an overall correction amount for the audio signal corrected by the static sound control integrated block based on the loudness correction according to the characteristics of the audio signal, as well as the noise level obtained by the same means as in the second embodiment.

[0104] The correction amount in the static audio control integrated block is calculated by referring to the Tone Table and the Loudness Table in addition to the Volume Tables and the AVC Tables.

[0105] Fig. 8 is a diagram showing a flow of a process for calculating a correction amount. Steps S201, S202, S203, S204, and S205 in Fig. 8 are processes for calculating a correction amount in the dynamic voice control integrated block.

[0106] Steps S301, S302, S303, S304 and S305 are processes for calculating the correction amount in the static audio control integrated block.

[0107] As shown in FIG. 8, the dynamic sound control integrated block detects the playback volume from the playback sound (step S201).

[0108] Then, the dynamic sound control integrated block calculates the loudness correction amount based on the detected playback volume (step S202).

[0109] The dynamic sound control integrated block also performs processing to collate the noise volume from the noise and vehicle speed signals obtained by microphone input (step S203).

[0110] Then, the dynamic sound control integrated block calculates the noise compensation correction amount based on the collated noise amount (step S204).

[0111] Furthermore, the dynamic voice control integrated block determines the correction amount A to be adopted from the correction amounts x1 and y1 calculated in steps S202 and S204, respectively (step S205).

[0112] Next, the static audio control integrated block checks the AVC Table based on the vehicle speed signal and the volume step (step S301).

[0113] Then, the static audio control integrated block calculates the masking avoidance correction amount (AVC correction amount) based on the result of matching with the AVC table (step S302).

[0114] In addition, the static sound control integrated block checks the Loudness Table based on the settings of tone control, etc. (step S303).

[0115] Then, the static sound control integrated block calculates the loudness correction amount based on the result of checking the loudness table (step S304).

[0116] Furthermore, the static sound control integrated block determines the correction amount B to be adopted from the correction amounts x2 and y2 calculated in steps S302 and S304, respectively (step S305).

[0117] Fig. 9 is a diagram for explaining the arbitration process of the correction amount. In the example of Fig. 9, it is assumed that in step S205 of Fig. 8, the correction amount x2 of the static loudness compensation is calculated to be 6 dB, and the correction amount y2 of the AVCEQ is calculated to be 4 dB.

[0118] In this case, since x2 is greater than y2, the static control correction amount arbitration unit 401 adopts x2 as the correction amount.

[0119] Moreover, the dynamic control correction amount arbitration unit 403 performs the same arbitration process as in FIG. 9 for x1 and y1.

[0120] In addition, the arbitration method is not limited to the one shown in Fig. 9, and may be a method of assigning weights to each calculation result. For example, when a weight of 2 is assigned to x1 and a weight of 1 is assigned to y1, the calculation is made as follows: A = (2 / 3) x1 + (1 / 3) y1.

[0121] By performing such arbitration processing, the correction amount calculated in each processing can be reflected in the final correction.

[0122] Further advantages and modifications may readily occur to those skilled in the art. Thus, the invention in its broader aspects is not limited to the specific details and representative embodiments shown and described above. Accordingly, various modifications may be made without departing from the spirit or scope of the general inventive concept as defined by the appended claims and equivalents thereof. [Explanation of symbols]

[0123] 1. Signal Processing Device 101 Volume control 102 User variable frequency characteristic correction section 103 Masking Avoidance Section 104 Playback volume level detection section 105 Dynamic loudness correction amount calculation unit 106 Dynamic loudness correction section 107 Static loudness correction section 108 Frequency characteristic correction section 201 Volume gain calculation unit 202 User variable frequency correction amount calculation unit 203 Masking avoidance correction amount calculation unit 204 Static loudness correction amount calculation unit

Claims

1. a first correction unit that corrects a frequency characteristic of an input audio signal in accordance with a content of a user setting and a state of a vehicle in which the audio signal is reproduced; a second correction unit that performs loudness correction by nonlinear processing to generate harmonic components on the audio signal corrected by the first correction unit, and further performs loudness correction by linear processing on the audio signal corrected by the nonlinear processing; A signal processing device comprising:

2. The signal processing device according to claim 1 , wherein the second correction unit performs loudness correction according to a level of the audio signal after the volume has been adjusted.

3. A first correction unit that corrects a frequency characteristic of an input audio signal according to a content of a user setting and a state of a vehicle in which the audio signal is reproduced; a second correction unit that performs loudness correction on the audio signal corrected by the first correction unit according to characteristics of the audio signal; a third correction unit that performs volume correction on the audio signal corrected by the second correction unit based on a noise amount collected by a microphone provided in the vehicle; A signal processing device comprising:

4. The signal processing device according to claim 3 , wherein the third correction unit performs correction using components for each band obtained by filtering a voice signal obtained by removing a reproduced sound component from a noise signal collected by the microphone.

5. A first correction unit that performs loudness correction by linear processing in addition to frequency characteristic correction for an input audio signal according to a user's settings and a state of a vehicle in which the audio signal is reproduced; a second correction unit that performs loudness correction on the audio signal corrected by the first correction unit in accordance with a characteristic of the audio signal, and also performs volume correction based on a noise amount collected by a microphone provided in the vehicle; A signal processing device comprising:

6. the first correction unit corrects the input audio signal with a correction amount calculated from a correction amount of a frequency characteristic according to a content of a user setting and a state of a vehicle in which the audio signal is reproduced, and a correction amount of a loudness correction by linear processing; 6. The signal processing device according to claim 5, wherein the second correction unit corrects the audio signal corrected by the first correction unit using a correction amount calculated from a loudness correction amount according to the characteristics of the audio signal and a volume correction amount based on the noise level.

7. A signal processing method performed by a signal processing device, comprising: a first correction step of correcting a frequency characteristic of an input audio signal in accordance with a content of a user setting and a state of a vehicle in which the audio signal is reproduced; a second correction step of performing loudness correction by nonlinear processing that generates harmonic components on the audio signal corrected by the first correction step, and further performing loudness correction by linear processing on the audio signal corrected by the nonlinear processing; A signal processing method comprising:

8. A signal processing method performed by a signal processing device, comprising: a first correction step of correcting a frequency characteristic of an input audio signal in accordance with a content of a user setting and a state of a vehicle in which the audio signal is reproduced; a second correction step of performing loudness correction on the audio signal corrected by the first correction step in accordance with characteristics of the audio signal; a third correction step of performing a volume correction on the audio signal corrected by the second correction step based on a noise amount collected by a microphone provided in the vehicle; A signal processing method comprising:

9. A signal processing method performed by a signal processing device, comprising: a first correction step of correcting a frequency characteristic of an input audio signal according to a user's setting and a state of a vehicle in which the audio signal is reproduced, and also correcting loudness by linear processing; a second correction step of performing loudness correction on the audio signal corrected by the first correction step in accordance with a characteristic of the audio signal, and also performing volume correction based on a noise amount collected by a microphone provided in the vehicle; A signal processing method comprising:

10. A signal processing system having a vehicle and a signal processing device, The signal processing device includes: a first correction unit that corrects a frequency characteristic of an input audio signal in accordance with a content of a user setting and a state of a vehicle in which the audio signal is reproduced; a second correction unit that performs loudness correction by nonlinear processing to generate harmonic components on the audio signal corrected by the first correction unit, and further performs loudness correction by linear processing on the audio signal corrected by the nonlinear processing; having The vehicle is a signal processing system further comprising an output section for converting the audio signal corrected by the second correction section into a sound and outputting the sound;

11. A signal processing system having a vehicle and a signal processing device, The signal processing device includes: a first correction unit that corrects a frequency characteristic of an input audio signal in accordance with a content of a user setting and a state of a vehicle in which the audio signal is reproduced; a second correction unit that performs loudness correction on the audio signal corrected by the first correction unit according to characteristics of the audio signal; a third correction unit that performs volume correction on the audio signal corrected by the second correction unit based on a noise amount collected by a microphone provided in the vehicle; having The vehicle is a signal processing system further comprising an output section for converting the audio signal corrected by the second correction section into a sound and outputting the sound;

12. A signal processing system having a vehicle and a signal processing device, The signal processing device includes: a first correction unit that performs loudness correction by linear processing on an input audio signal in addition to correcting a frequency characteristic according to a content of a user setting and a state of a vehicle in which the audio signal is reproduced; a second correction unit that performs loudness correction on the audio signal corrected by the first correction unit in accordance with a characteristic of the audio signal, and also performs volume correction based on a noise amount collected by a microphone provided in the vehicle; having The vehicle is a signal processing system further comprising an output section for converting the audio signal corrected by the second correction section into a sound and outputting the sound;

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