Title of Invention: INFORMATION PROCESSING APPARATUS, INFORMATION PROCESSING METHOD, AND RECORDING MEDIUM Abstract: To provide a mechanism for selectively taking an external sound from an appropriate sound source into an internal space of a moving object. An information processing apparatus including an acquisition unit configured to acquire an audio signal from a sound source existing outside a moving object, a generation unit configured to generate an audio signal from a target sound source at a distance from the moving object, the distance being a distance according to a speed of the moving object, of the sound sources, on the basis of the audio signal acquired by the acquisition unit, and an output control unit configured to output the audio signal generated by the generation unit toward an internal space of the moving object. Detailed Description: TECHNICAL FIELD The present disclosure relates to an information processing apparatus, an information processing method, and a recording medium. BACKGROUND ART In recent years, while technologies for securing low noise such as noise canceling technology have been improved, adverse effects of the improvement of low noise have been pointed out. For example, in a case where a user wears headphones and walks in a city while listening to music, it is difficult to hear an external sound from a sound sources present in surroundings. Therefore, for example, it has been pointed out that the user does not notice approaching of a car, which is dangerous, the user is isolated from the surroundings and gets a cooped-up feeling, and the like. As a countermeasure against such indication, for example, Patent Document 1 below discloses a technology for reducing the cooped-up feeling felt by the user by taking an external sound in headphones. CITATION LIST Patent Document Patent Document 1: Japanese Patent Application Laid-Open No. (839)207-6787 SUMMARY OF THE INVENTION Problems to be Solved by the Invention Occurrence of similar circumstances is conceivable in moving objects such as cars. For example, while sound insulation performance of a car body has been dramatically improved in order to reduce an influence of engine noise and running noise of a car on an internal space, adverse effect such as occurrence of danger or a cooped-up feeling due to inability to hear an external sound has occurred. Therefore, the present disclosure provides a mechanism for selectively taking an external sound from an appropriate sound source into an internal space of a moving object. Solutions to Problems According to the present disclosure, provided is an information processing apparatus including an acquisition unit configured to acquire an audio signal from a sound source existing outside a moving object, a generation unit configured to generate an audio signal from a target sound source at a distance from the moving object, the distance being a distance according to a speed of the moving object, of the sound sources, on the basis of the audio signal acquired by the acquisition unit, and an output control unit configured to output the audio signal generated by the generation unit toward an internal space of the moving object. Furthermore, according to the present disclosure, provided is an information processing method including acquiring an audio signal from a sound source existing outside a moving object, generating an audio signal from a target sound source at a distance from the moving object, the distance being a distance according to a speed of the moving object, of the sound sources, on the basis of the acquired audio signal, and outputting, by an output device, the generated audio signal toward an internal space of the moving object. Furthermore, according to the present disclosure, provided is a recording medium having a program recorded, the program for causing a computer to function as an acquisition unit configured to acquire an audio signal from a sound source existing outside a moving object, a generation unit configured to generate an audio signal from a target sound source at a distance from the moving object, the distance being a distance according to a speed of the moving object, of the sound sources, on the basis of the audio signal acquired by the acquisition unit, and an output control unit configured to output the audio signal generated by the generation unit toward an internal space of the moving object. According to the present disclosure, a signal generated on the basis of an audio signal acquired from a sound source present outside a moving object is output toward an internal space of the moving object. Thereby, the external sound can be taken into the internal space of the moving object. Furthermore, an external sound from an appropriate sound source according to a speed of the moving object can be selectively taken in. Effects of the Invention As described above, according to the present disclosure, provided is a mechanism for selectively taking an external sound from an appropriate sound source into an internal space of a moving object. Note that the above-described effect is not necessarily restrictive, and any one of effects described in the present specification or any another effect obtainable from the present specification may be exhibited in addition to or in place of the above-described effect. BRIEF DESCRIPTION OF DRAWINGS FIG. 1 is a diagram for describing an example of an information processing apparatus according to an embodiment of the present disclosure. FIG. 2 is a block diagram illustrating an example of a logical configuration of the information processing apparatus according to the present embodiment. FIG. 3 is a diagram for describing an example of setting of an operation mode according to the present embodiment. FIG. 4 is a diagram for describing an example of processing of determining a distance between a moving object and a sound source according to the present embodiment. FIG. 5 is a diagram for describing an example of the processing of determining a distance between a moving object and a sound source according to the present embodiment. FIG. 6 is a diagram for describing an example of signal processing by the information processing apparatus according to the present embodiment. FIG. 7 is a diagram for describing an example of howling suppression processing according to the present embodiment. FIG. 8 is a diagram for describing an example of external sound signal separation/selection processing according to the present embodiment. FIG. 9 is a diagram for describing an example of external sound signal correction processing according to the present embodiment. FIG. 10 is a diagram for describing an example of the signal processing by the information processing apparatus according to the present embodiment. FIG. 11 is a diagram for describing an example of the signal processing by the information processing apparatus according to the present embodiment. FIG. 12 is a diagram for describing an example of the signal processing by the information processing apparatus according to the present embodiment. FIG. 13 is a diagram for describing an example of processing of releasing an internal sound into a space outside a car according to the present embodiment. FIG. 14 is a block diagram illustrating an example of a schematic configuration of a vehicle system. MODE FOR CARRYING OUT THE INVENTION Favorable embodiments of the present disclosure will be described in detail with reference to the appended drawings. Note that, in the present specification and drawings, redundant description of configuration elements having substantially the same functional configuration is omitted by providing the same sign. Note that the description will be given in the following order. 1. Overview 2. Functional Configuration 3. Technical Characteristics 3.1. Acquisition of Audio Signal 3.2. Setting of Operation Mode 3.3. Selection of Target Sound Source 3.4. Generation of Audio Signal 3.5. Output of Audio Signal 4. Specific Signal Processing Example 5. Supplement 6. Application 7. Conclusion <<1. Overview>> FIG. 1 is a diagram for describing an example of an information processing apparatus according to an embodiment of the present disclosure. As illustrated in FIG. 1, a moving object 10 is traveling around sound sources 20A and 20B. The moving object 10 has an internal space that is a space for a person to stay in the moving object 10. The moving object 10 illustrated in FIG. 1 is provided with a seat in the internal space, and a driver, a passenger, and the like can stay in the internal space. In the example illustrated in FIG. 1, the moving object 10 is a car. The moving object 10 may be any moving object having an internal space where a person stays, and may be, for example, a construction vehicle, a ship, an airplane, a train, a vehicle in an amusement park, playground equipment, or the like. The sound source 20A is a clock tower and sounds a time signal on time. The sound source 20B is a pedestrian and suddenly emits speech, footsteps, and the like. However, the sounds in a space outside the car (hereinafter also referred to as external sounds) are difficult for a person in the car to hear because the internal space of the car 10 is isolated from an external space. Note that, hereinafter, the internal space of the moving object 10 is also referred to as a space inside the car, and the external space is also referred to as a space outside the car. Therefore, the information processing apparatus according to the present embodiment performs processing of reproducing an external sound toward the space inside the car, in other words, taking the external sound into the space inside the car. For example, the information processing apparatus according to the present embodiment detects an external sound by microphones 110A to 110D, applies predetermined signal processing to an audio signal representing the detected external sound, and outputs the audio signal to the space inside the car by speakers 120A to 120D. With the configuration, with regard to a car, a sound environment that provides a realistic feeling as if there were no car wall can be realized in the space inside the car. Taking in of the external sound can be performed for driving assistance applications, for example. A driver can get to know a surrounding situation as the external sound is taken into the internal space. For example, the driver listens to the sound of the pedestrian 20B and can prevent an accident by slowing down in preparation for jumping out of the pedestrian 20B to the road. Taking in of the external sound can also be performed for entertainment applications, for example. For example, in a vehicle covered with glass for securing the weather and safety, such as a dedicated car in a safari park, the sound pressure and characteristics of the external sound change due to the influence of the glass, and the realistic feeling is significantly lost. In such a case, by taking in the external sound, a sound environment as if there were no glass is realized, and a person in the space inside the car can enjoy an experience that provides a realistic feeling. Note that the information processing apparatus according to the present embodiment is realized as a server apparatus mounted on a moving object or capable of communicating with the moving object, and controls processing of taking in the external sound. Hereinafter, description will be given on the assumption that the information processing apparatus according to the present embodiment is mounted on the moving object 10. <<2. Functional Configuration>> FIG. 2 is a block diagram illustrating an example of a logical configuration of the information processing apparatus according to the present embodiment. As illustrated in FIG. 2, an information processing apparatus 100 according to the present embodiment includes a sensor unit 110, an output unit 120, a communication unit 130, a storage unit 140, and a processing unit 150. (1) Sensor Unit 110 The sensor unit 110 has a function to detect various types of information. The sensor unit 110 outputs detected sensor information to the processing unit 150. The sensor unit 110 may include a sensor that detects information of the external space of the moving object. For example, the sensor unit 110 detects the external sound as the information of the external space of the moving object. The sensor that detects the external sound can include a plurality of microphones such as the microphones 110A to 110D illustrated in FIG. 1. Of course, there may be only one microphone. The microphone for detecting the external sound is installed in the moving object in a state where at least a part of the configuration, typically, such as a diaphragm, is exposed to the external space (in other words, in a state of being in contact with outside air). For example, the microphone for detecting the external sound is installed on an outer wall of the car body. In addition, the sensor unit 110 may detect a captured image, depth information, an infrared image, or the like as the information of the external space of the moving object. The sensor unit 110 can include a sensor that detects information regarding a state of the moving object. For example, the sensor unit 110 detects speed, acceleration, position information, or the like of the moving object as the information regarding a state of the moving object. The sensor unit 110 can include a sensor that detects information of the internal space of the moving object. For example, the sensor unit 110 detects input information by a person in the internal space, voice, a captured image, biological information, or the like as the information of the internal space of the moving object. The sensor unit 110 can include a clock that detects time information. (2) Output Unit 120 The output unit 120 has a function to output various types of information. The output unit 120 outputs information on the basis of control by the processing unit 150. The output unit 120 can output information to the internal space of the moving object. For example, the output unit 120 can include a plurality of speakers, such as the speakers 120A to 120D illustrated in FIG. 1. Of course, there may be only one speaker. The speaker is typically installed in the space inside the car, such as an inside of a door. In addition, the output unit 120 may output an image (a still image or a moving image), vibration, or the like. (3) Communication Unit 130 The communication unit 130 has a function to transmit and receive signals to and from other devices. For example, the communication unit 130 can communicate using any communication standard such as cellular communication such as 4G or 5G, a wireless local area network (LAN), Wi-Fi (registered trademark), or Bluetooth (registered trademark). In particular, in a case where the moving object is a car, the communication unit 130 can communicate using vehicle to everything (V2X) communication. (4) Storage Unit 140 The storage unit 140 has a function to temporarily or permanently store information for the operation of the information processing apparatus 100. For example, the storage unit 140 stores known sound source information to be described below. (5) Processing Unit 150 The processing unit 150 provides various functions of the information processing apparatus 100. The processing unit 150 includes an acquisition unit 151, a setting unit 153, a generation unit 155, and an output control unit 157. Note that the processing unit 150 can further include other configuration elements in addition to the aforementioned configuration elements. In other words, the processing unit 150 can also perform operations other than the operations of the aforementioned configuration elements. The functions of the configuration elements of the acquisition unit 151, the setting unit 153, the generation unit 155, and the output control unit 157 will be described in detail below. <<3. Technical Characteristics>> <3.1. Acquisition of Audio Signal> First, the information processing apparatus 100 (for example, the acquisition unit 151) acquires an audio signal (in other words, a signal representing an external sound) from a sound source existing outside the moving object. For example, the information processing apparatus 100 acquires an audio signal of a sound that is actually sounding at the sound source existing outside the moving object, which is detected by the microphones 110A to 110D illustrated in FIG. 1. <3.2. Setting of Operation Mode> After acquiring the audio signal, the information processing apparatus 100 (for example, the setting unit 153) sets an operation mode. The information processing apparatus 100 (setting unit 153) selects and sets an operation mode from an operation mode group including a plurality of operation modes. Hereinafter, an example of the operation mode included in the operation mode group will be described. (1) Operation Mode Group The operation mode group may include a first operation mode in which an output to the internal space of the moving object is not performed. The information processing apparatus 100 operates in the first operation mode to stop taking the external sound into the space inside the car. The operation mode group may include a second operation mode in which an output to the internal space of the moving object is performed. The information processing apparatus 100 operates in the second operation mode to perform taking the external sound into the space inside the car. The second operation mode can be subdivided into third to fifth operation modes to be described below. The second operation mode may include the third operation mode for a known sound source as a target sound source. The information processing apparatus 100 operates in the third operation mode to perform taking the external sound from the known sound source into the space inside the car. The known sound source is a sound source that emits a sound according to a predetermined condition. Examples of the known sound source include sound sources that emit sounds as scheduled according to conditions such as a place and a time, such as the clock tower 20A illustrated in FIG. 1, a fireworks display, and a railroad crossing. In the third operation mode, sounds such as a sound from a clock tower in a tourist attraction or a crossing noise can be taken into the space inside the car. Therefore, it can be said that the third operation mode is effective for driving assistance applications and entertainment applications. The second operation mode may include the fourth operation mode for an unknown sound source as the target sound source. The information processing apparatus 100 operates in the fourth operation mode to perform taking the external sound from the unknown sound source into the space inside the car. The unknown sound source is a sound source that suddenly emits a sound. As the unknown sound source, for example, the pedestrian 20B illustrated in FIG. 1, an oncoming car, or the like can be considered. In the fourth operation mode, a sound that suddenly occurs, such as a sound of a pedestrian and an oncoming car can be taken into the space inside the car. Therefore, the fourth operation mode is particularly effective for driving assistance applications. The second operation mode may include the fifth operation mode for the known sound source and the unknown sound source as the target sound sources. The information processing apparatus 100 operates in the fifth operation mode to perform taking the external sounds from both the known sound source and the unknown sound source into the space inside the car. (2) Setting of Operation Mode The information processing apparatus 100 (for example, the setting unit 153) can set (in other words, switch) the operation mode on the basis of various criteria. External Sound The information processing apparatus 100 may set the operation mode on the basis of the audio signal from the sound source existing outside the moving object. Specifically, the information processing apparatus 100 can switch between the first operation mode and the second operation mode according to the presence, the size, the type, or the like of the external sound. Known Sound Source Information The information processing apparatus 100 may set the operation mode on the basis of the known sound source information. The known sound source information can include map information, for example, and the information processing apparatus 100 may set the operation mode on the basis of the map information indicating the position of the known sound source and position information of the moving object. The map information includes information indicating a range in which the sound from the known sound source should be taken in. For example, the range in which the sound from the known sound source should be taken in may be defined as the position of the known sound source and a circle centered on the position. In this case, the information indicating the range in which the sound from the known sound source should be taken in includes position information of the known sound source and distance information of a radius of the circle. An example of operation mode setting based on the map information will be described with reference to FIG. 3. FIG. 3 is a diagram for describing an example of setting of an operation mode according to the present embodiment. FIG. 3 illustrates an example of map information 30, and the map information 30 includes position information indicating a position 31 of the known sound source, and information indicating a range 32 within a predetermined distance from the known sound source. For example, the information processing apparatus 100 sets the third operation mode in a case where the moving object is located within the range 32 and sets the fourth operation mode in a case where the moving object is located outside the range 32 with reference to the map information 30. The map information may further include information indicating the time zone in which the known sound source emits the sound. In this case, the information processing apparatus 100 sets the operation mode on the further basis of the current time. For example, in a case where the moving object is located within the range in which the sound from the known sound source should be taken in and the current time is included in a time zone in which the known sound source emits the sound, the information processing apparatus 100 sets the third operation mode. Thereby, the information processing apparatus 100 can take the sound from the known sound source into the space inside the car in a pinpoint manner in time with the time zone in which the known sound source emits the sound. Furthermore, the map information may include information indicating types of roads such as general roads, expressways, elevated roads, and underground roads, and the information processing apparatus 100 may set the operation mode on the basis of such information. The known sound source information may include an additional sound. The additional sound is an audio signal associated with the known sound source and is stored in advance in the storage unit 140, or an external server apparatus or the like. The information processing apparatus 100 acquires, in the third mode or the fifth mode, the previously stored additional sound related to the known sound source and outputs the additional sound. The additional sound is, for example, description regarding the known sound source such as a history of the clock tower 20A in the example illustrated in FIG. 1, a sound effect in an amusement park, or the like. For example, in the example illustrated in FIG. 1, in a case where the car 10 is located within a predetermined distance from the clock tower 20A in the time zone in which the clock tower 20A emits the sound, the information processing apparatus 100 outputs the sound describing the history of the clock tower 20A while taking the sound actually emitted from the clock tower 20A into the space inside the car. In this way, the aspect of entertainment in the entertainment applications can be enhanced by the additional sound. Note that a storage location of the known sound source information is arbitrary. For example, the known sound source information may be stored in the information processing apparatus 100 or may be stored in a server apparatus on the Internet. Furthermore, the map information may be stored in the information processing apparatus 100 and the additional sound may be stored in the server apparatus, among the known sound source information, and may be downloaded as needed. Information from External Device The information processing apparatus 100 may set the operation mode on the basis of the information from an external device. For example, the external device may be a car, a device carried by a pedestrian, or a device capable of vehicle to everything (V2X) communication such as a road side unit (RSU). For example, the information processing apparatus 100 recognizes the presence of a car traveling in a driver's blind area on the basis of information from the RSU, sets the fourth operation mode, and takes the sound from the car into the space inside the car, thereby preventing an accident in advance. User Operation The information processing apparatus 100 may set the operation mode on the basis of a user operation. For example, the information processing apparatus 100 may set the operation mode according to a selection operation of the operation mode by the user. <3.3. Selection of Target Sound Source> After setting of the operation mode, the information processing apparatus 100 (for example, the generation unit 155) selects a sound source that will be a target from which a sound will be taken into the space inside the car, as a target sound source, from sound sources (the unknown sound source and/or the known sound source) existing around the moving object according to the set operation mode. Of course, all of the sound sources may be selected as the target sound sources. Note that, in the third mode or the fifth mode, there may be cases where the known sound source is not selected as the target sound source or the known sound source is always selected as the target sound source. Selection criteria of the target sound source can be variously considered. Examples will be described below. The information processing apparatus 100 may use one or a plurality of the determination criteria described below in combination. Distance The information processing apparatus 100 may select a sound source at a distance from the moving object, the distance being according to the speed of the moving object, from among the sound sources, as the target sound source. Specifically, the information processing apparatus 100 selects the sound source farther from the moving object as the speed of the moving object is higher as the target sound source, and selects the sound source closer to the moving object as the speed of the moving object is lower as the target sound source. Typically, in a case where a car speed is high, the moving object is immediately away from a nearby sound source, so it is conceivable that a sound from a distant sound source is more useful. Meanwhile, in a case where the car speed is low, it takes time to approach a distant sound source, so it is conceivable that a sound from a nearby sound source is more useful. The information processing apparatus 100 can take a more useful sound into the space inside the car by setting the sound source at a distance according to the speed of the moving object as the target sound source. Determination criteria of the distance between the moving object and the sound source can be variously considered. Hereinafter, examples will be described with reference to FIGS. 4 and 5. Note that the information processing apparatus 100 may use one or a plurality of the determination criteria described below in combination. FIGS. 4 and 5 are diagrams for describing examples of processing of determining the distance between the moving object and the sound source according to the present embodiment. FIGS. 4 and 5 illustrate a position 41 at a certain time (hereinafter also referred to as a reference time) of the moving object 10, a position 42 after t seconds from the reference time, and the sound source 20A close to the moving object 10 and the sound source 20B distant from the moving object 10 at the reference time. Then, FIG. 4 is an example of a case where the speed of the moving object 10 is high, and FIG. 5 is an example of a case where the speed of the moving object 10 is low. For example, the information processing apparatus 100 may determine the distance between the moving object and the sound source on the basis of time-series change in an azimuth of the sound source with reference to the moving object. Referring to FIG. 4, in a case where the speed of the moving object 10 is high, the time-series change (from an angle 43 to an angle 44) during t seconds in the azimuth of the sound source 20A with reference to the moving object 10 is large. Furthermore, referring to FIG. 4, in the case where the speed of the moving object 10 is high, the time-series change (from an angle 45 to an angle 46) during t seconds in an azimuth of the sound source 20B with reference to the moving object 10 is small. Therefore, in the case where the speed of the moving object 10 is high, the information processing apparatus 100 can determine that the distance to the sound source having large time-series change in the azimuth with reference to the moving object is small, and can determine that the distance to the sound source having small time-series change is large. Note that determination of identity of the sound source at the reference time and the time after t seconds may be performed on the basis of spectral shapes of the sounds, for example. For example, the information processing apparatus 100 may determine the distance between the moving object and the sound source on the basis of time-series change in sound pressure from the sound source. Referring to FIG. 4, in the case where the speed of the moving object 10 is high, the time-series change during t seconds in the sound pressure from the sound source 20A is large because the distance between the moving object 10 and the sound source 20A largely changes. Furthermore, referring to FIG. 4, in the case where the speed of the moving object 10 is high, the time-series change during t seconds in the sound pressure from the sound source 20B is small because the distance between the moving object 10 and the sound source 20B does not much change. Therefore, in the case where the speed of the moving object 10 is high, the information processing apparatus 100 can determine that the distance to the sound source having large time-series change in the sound pressure is small, and can determine that the distance to the sound source having small time-series change is large. Here, referring to FIG. 5, in a case where the speed of the moving object 10 is low, it can be considered that there is a small difference in the time-series change in the azimuth of the sound source and in the time-series change in the sound pressure between the sound source at the large distance and the sound source at the small distance to the moving object. Specifically, in the case where the speed of the moving object 10 is low, the time-series change (from the angle 43 to the angle 44) during t seconds in the azimuth of the sound source 20A with reference to the moving object 10 is small, and the time-series change (from the angle 45 to the angle 46) during t seconds in the azimuth of the sound source 20B is also small. Furthermore, in the case where the speed of the moving object 10 is low, the time-series change during t seconds in the sound pressure from the sound source 20A is small because the distance between the moving object 10 and the sound source 20A does not much change, and the time-series change during t seconds in the sound pressure from the sound source 20B is also small because the distance between the moving object 10 and the sound source 20B does not much change. Therefore, the information processing apparatus 100 may determine the distance between the moving object and the sound source on the basis of an absolute value of the sound pressure from the sound source. For example, it can be considered that the absolute value of the sound pressure is larger as the distance between the moving object and the sound source is smaller, and the absolute value of the sound pressure is smaller as the distance is smaller. Therefore, the information processing apparatus 100 can determine the distance between the moving object and the sound source by referring to the absolute value of the sound pressure in the case where the speed of the moving object is low. Of course, the information processing apparatus 100 can increase determination accuracy by referring to the absolute value of the sound pressure even in the case where the speed of the moving object is high. Note that, in the above-description, it has been described that the information processing apparatus 100 selects a sound source at a distance from the moving object, the distance being according to the speed of the moving object, from among the sound sources, as the target sound source. However, the speed of the moving object here may be a relative speed to the sound source. For example, in a case where the relative speed is small because the moving object and the sound source travel in parallel, the information processing apparatus 100 can determine the distance to the moving object by the determination criterion of the case where the speed of the moving object is low. Furthermore, in a case where the relative speed is large because the moving object and the sound source travel opposite to each other, for example, the information processing apparatus 100 can determine the distance to the moving object by the determination criterion of the case where the speed of the moving object is high. Type The information processing apparatus 100 may select whether or not to set the sound source as the target sound source according to the type of the sound source. For example, the information processing apparatus 100 selectively takes human voice into the space inside the car and does not take music that sounds outside the car into the space inside the car. With such switching, the information processing apparatus 100 can selectively take only the sound to be taken into the space inside the car. Target The information processing apparatus 100 may select whether or not to set the sound source as the target sound source according to whether or not the target of the sound from the sound source is the moving object. For example, the information processing apparatus 100 selectively takes a horn honking at the moving object into the space inside the car, and does not take the horn honking at another car into the space inside the car. Such switching cab be performed on the basis of, for example, the direction of the car that has honked the horn or the like. With such switching, the information processing apparatus 100 can selectively take only the sound to be taken into the space inside the car. <3.4. Generation of Audio Signal> After selection of the target sound source, the information processing apparatus 100 (for example, the generation unit 155) generates the audio signal from the target sound source on the basis of the acquired audio signal. Generation of the audio signal from the target sound source can be performed by applying so-called beamforming processing to the acquired audio signal. For example, the information processing apparatus 100 may apply signal processing of canceling sounds other than the sound from the target sound source to the acquired audio signal. Furthermore, the information processing apparatus 100 may apply sound processing of emphasizing the sound from the target sound source to the acquired audio signal. Note that, as described above, in the third or the fifth operation mode, the information processing apparatus 100 may use the additional sound in place of or in addition to the generation by the signal processing, as the audio signal from the target sound source <3.5. Output of Audio Signal> After generation of the audio signal from the target sound source, the information processing apparatus 100 (for example, the output control unit 157) causes the generated audio signal to be output toward the internal space of the moving object. For example, the information processing apparatus 100 outputs the generated audio signal by the speakers 120A to 120D illustrated in FIG. 1. <<4. Specific Signal Processing Example>>vHereinafter, an example of specific signal processing will be described with reference to FIGS. 6 to 12. (1) First Example FIG. 6 is a diagram for describing an example of signal processing by the information processing apparatus 100 according to the present embodiment. As illustrated in FIG. 6, the information processing apparatus 100 inputs, to a howling suppression unit 161, a plurality of audio signals detected by the plurality of microphones (for example, microphone array) included in the sensor unit 110. Howling Suppression Unit 161 The howling suppression unit 161 performs processing of suppressing howling. Howling is a phenomenon of oscillation due to formation of a feedback loop in which a signal emitted from a speaker is input again to a microphone. The howling suppression processing will be described with reference to FIG. 7. FIG. 7 is a diagram for describing an example of the howling suppression processing according to the present embodiment. As illustrated in FIG. 7, the howling suppression processing by the howling suppression unit 161 is applied to the audio signal input from the microphone 110, signal processing by a signal processing unit 201 is applied to the audio signal, the audio signal is amplified by an amplifier 175A or 175B, and the audio signal is output from the speaker 120. Note that, in FIG. 7, other signal processing illustrated in FIG. 6 is simplified or omitted, and the signal processing unit 201 includes a wind noise removal unit 162 illustrated in FIG. 6 and the like. The howling suppression unit 161 measures a space transfer function H in advance. Then, the howling suppression unit 161 monitors a signal X reproduced from the speaker 120, and estimates a signal Y that is the signal X passing through the space transfer function H and entering the microphone 110 again. The howling suppression unit 161 analyzes a frequency characteristic of the signal Y, and suppresses a signal in a band exceeding a specified value in a case where a gain of the signal Y to be fed back exceeds a specified value, thereby suppressing howling. For example, the howling suppression unit 161 applies a notch filter to suppress the signal in the band exceeding the specified value. Note that, in a case where suppression of the howling by the notch filter is difficult, the howling suppression unit 161 stops the reproduction or lowers the gain to suppress the howling. Wind Noise Removal Unit 162 As illustrated in FIG. 6, the information processing apparatus 100 inputs the signal after application of the howling suppression processing to the wind noise removal unit 162. The wind noise removal unit 162 performs processing of removing wind noise. Wind pressure removal may be performed by a fixed filter. The wind noise has a characteristic that energy is concentrated in a low frequency band. Therefore, the wind noise removal unit 162 applies a high pass filter, which decrease 200 to 300 Hz or less, to the signal, thereby removing the wind noise. The wind noise removal may be performed by signal processing. Because the wind noise is caused by air turbulence generated near the microphone rather than a sound wave, different noise is input to each microphone. In other words, correlation between the microphones is characterized by low in the wind noise and high in normal sound waves. Therefore, the wind noise removal unit 162 can dynamically remove the wind noise by performing processing of calculating the correlation between microphones for each frequency band, determining that the wind noise exists when a correlation value falls below a certain threshold value, and lowering the gain in the time and the band in which the wind noise exists. Processing Group 170 As illustrated in FIG. 6, the information processing apparatus 100 performs each processing included in a processing group 170 after applying the wind noise removal processing. The processing in the processing group 170 differs depending on the set operation mode. The processing group 170 illustrated in FIG. 6 includes the processing executed in the fifth operation mode. Known Sound Source Control Unit A known sound source control unit 171 controls signal processing related to the known sound source. Specifically, the known sound source control unit 171 controls an external sound signal separation/selection unit 173A, an external sound signal correction filter 174A, and the amplifier 175A on the basis of the position information, the time, and the map information of known sound source information 172. Note that the signal input to the processing group 170 passes through the external sound signal separation/selection unit 173A, the external sound signal correction filter 174A, and the amplifier 175A in order. Note that the known sound source control unit 171 may realize the operation in the first operation mode or the fourth operation mode by setting an amplification amount by the amplifier 175A to (in other words, setting amplitude to 0) to stop reproduction of the signal related to the known sound source. Unknown Sound Source Control Unit An unknown sound source control unit 176 controls signal processing regarding the unknown sound source. Specifically, the unknown sound source control unit 176 controls an external sound signal separation/selection unit 173B, an external sound signal correction filter 174B, and the amplifier 175B on the basis of the car speed (in other words, the speed of the moving object) and microphone sound pressure. Note that the signal input to the processing group 170 passes through the external sound signal separation/selection unit 173B, the external sound signal correction filter 174B, and the amplifier 175B in order. Note that the unknown sound source control unit 176 may realize the operation in the first operation mode or the third operation mode by setting an amplification amount by the amplifier 175B to (in other words, setting amplitude to 0) to stop reproduction of the signal related to the unknown sound source. External Sound Signal Separation/Selection Unit The external sound signal separation/selection unit 173 (173A or 173B) performs separation and/or selection of an external sound signal (the audio signal of the external sound). The external sound signal separation/selection unit 173 can adopt conventionally known beamforming technology or sound source separation technology. Hereinafter, an example will be described with reference to FIG. 8. FIG. 8 is a diagram for describing an example of the external sound signal separation/selection processing according to the present embodiment. As illustrated in FIG. 8, sound sources 20A, 20B, and 20C exist around the moving object 10. There are the following first to third methods, for example, as the sound source separation technology using two or more microphones. The first method is a method of extracting a specific sound on the basis of directionality. According to the first method, for example, only the sound source 20A can be extracted. The first method is, for example, delayed beam forming (delay and sum beamforming (DS)). The second method is a method of removing a specific sound on the basis of directionality. According to the second method, for example, only the sound source 20A can be removed, and the sound sources 20B and 20C can be extracted. The second method is, for example, blind area controlled beamforming (null beamforming (NBF)). The third method is a method of separating a sound to be statistically independent from an obtained signal although sound source characteristics are unknown. According to the third method, the sound sources 20A, 20B, and 20C can be individually extracted. The third method is, for example, independent component analysis (ICA). There is the following fourth method, for example, as the sound source separation technology using one, or two or more microphones. The fourth method is a method of extracting each sound source on the basis of spectral characteristics of the sound source. According to the fourth method, the sound sources 20A, 20B, and 20C can be individually extracted. The fourth method is, for example, non-negative matrix factorization (NMF). In the above, examples of the beamforming technology and the sound source separation technologies have been described. For example, the external sound signal separation/selection unit 173A calculates, with regard to the known sound source, the direction in which the known sound source to be acquired exists, using the position information and the map information of the moving object 10. Furthermore, the external sound signal separation/selection unit 173B estimates, with regard to the unknown sound source, the direction in which the unknown sound source exists on the basis of a phase difference of the input signal. Next, the external sound signal separation/selection unit 173 calculates a coefficient of the delayed beamforming in order to acquire the sound in the direction acquired by the calculation. Then, the external sound signal separation/selection unit 173 multiplies the microphone input by the coefficient of the delayed beamforming and outputs the audio signal of the known sound source or the unknown sound source to be acquired to the external sound signal correction filter 174. External Sound Signal Correction Filter The external sound signal correction filter 174 (174A or 174B) performs processing of correcting the external sound signal. External sound signal correction processing by an external sound signal correction filter will be described with reference to FIG. 9. FIG. 9 is a diagram for describing an example of external sound signal correction processing according to the present embodiment. As illustrated in FIG. 9, an input signal S detected by the microphone 110 passes through the external sound signal correction filter 174, the amplifier 175, and the speaker 120, and is reproduced as a reproduction signal Z. Note that, in FIG. 9, other signal processing illustrated in FIG. 6 is simplified or omitted. Since the input signal S passes through the above-described path and becomes the reproduction signal Z, the reproduction signal Z becomes a signal having the characteristic of the path. The reproduction signal Z can be expressed by the following expression, where a microphone characteristic is M, a filter characteristic is G, an amplifier characteristic is A, and a speaker characteristic is D. Z=SMGAD (1) The external sound signal correction filter is a filter that corrects the reproduction signal Z to be the same as the input signal S. Therefore, a filter coefficient G is expressed by the following expression, where Z=X is set to the above expression (1). G=1/MAD (2) As such, it is the external sound signal correction filter that cancels the characteristic MAD. These characteristics are obtained by preliminary measurement, and the filter coefficients are also preset. Amplifier The amplifier 175 (175A or 175B) amplifies and outputs the input signal. The amplification amount is controlled by the known sound source control unit 171 or the unknown sound source control unit 176. Adder 163 As illustrated in FIG. 6, the information processing apparatus 100 adds the signal to which the processing regarding the known sound source has been applied and the signal to which the processing regarding the unknown sound source has been applied, the pieces of processing having been input from the processing group 170, by an adder 163. Audio Mixer 164 An audio mixer 164 adds a predetermined signal to the signal for taking the external sound, via an adder 165. Examples of the predetermined signal here include an additional sound included in the known sound source information 172, a navigation sound signal output from a car navigation apparatus, an audio signal output from a music reproduction apparatus, and the like. The information processing apparatus 100 outputs the audio signal for which the above-described series of processing has been performed from the speaker 120. (2) Third Operation Mode with NC Function FIG. 10 is a diagram for describing an example of the signal processing by the information processing apparatus 100 according to the present embodiment. FIG. 10 illustrates signal processing in the third operation mode with noise canceling (NC) function. As illustrated in FIG. 10, in the third operation mode with the NC function, the blocks related to the unknown sound source (in other words, the unknown sound source control unit 176, the external sound signal separation/selection unit 173B, the external sound signal correction filter 174B, and the amplifier 175B) are deleted from the signal processing in the above-described fifth operation mode with reference to FIG. 6. Meanwhile, as illustrated in FIG. 10, in the third operation mode with the NC function, an NC control unit 177 and an NC filter 178 as blocks for signal processing for noise canceling are added.
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