1. A display apparatus for visual and audio multiplexed display, the display apparatus comprising: a directive display unit configured to display on a screen a plurality of pieces of visual information toward a corresponding plurality of locations, wherein each of the plurality of pieces of visual information is output toward a specific location of the plurality of locations; a directive speaker unit configured to transmit a plurality of pieces of audio information toward the plurality of locations, wherein each of the plurality of pieces of audio information is output toward a specific location of the plurality of locations; and a central control unit configured to control the directive display unit and the directive speaker unit, wherein the directive speaker unit comprises: at least one sound wave generator configured to generate a wave, wherein the wave is at least one of a sound wave and an ultrasound wave carrying the plurality of pieces of audio information, the at least one sound wave generator comprising a first sound wave generator that generates a first wave corresponding to a first piece of audio information, and a second sound wave generator that generates a second wave corresponding to a second piece of audio information; at least one acoustic meta-structure body having directivity and configured to at least one of collimate the wave generated by the at least one sound wave generator toward one direction, diverge the wave generated by the sound wave generator by a radiation angle within about 30°, and converge the wave generated by the sound wave generator into one point, and the at least one acoustic meta-structure body comprises a first acoustic meta-structure body that transmits the first wave generated by the first sound wave generator toward a first direction corresponding to the first piece of audio information, and a second acoustic meta-structure body that transmits the second wave generated by the second sound wave generator toward a second direction corresponding to the second piece of audio information.
2. The display apparatus of claim 1 , wherein the at least one acoustic meta-structure body comprises: a plurality of meta-units having a structure of a coil shape configured to shape a traveling path of the wave generated by the sound wave generator.
3. The display apparatus of claim 2 , wherein each of the plurality of meta-units comprises: an incident part that receives a wave; an output part that outputs the wave; and a plurality of channels forming a traveling path for the wave, wherein the plurality of channels are disposed between the incident part and the output part, and are connected to one another.
4. The display apparatus of claim 3 , wherein a linear distance between the incident part and the output part is shorter than a wavelength of the wave generated by the sound wave generator.
5. The display apparatus of claim 3 , wherein the plurality of channels are formed by a plate structure that partitions an air space in each of the plurality of meta-units.
6. The display apparatus of claim 2 , wherein each of the plurality of meta-units included in the acoustic meta-structure body have a same structure.
7. The display apparatus of claim 6 , wherein the acoustic meta-structure body has a structure in which a refractive index is near zero in a wavelength band of the wave generated by the sound wave generator.
8. The display apparatus of claim 7 , wherein the at least one sound wave generator is disposed inside the acoustic meta-structure body.
9. The display apparatus of claim 7 , wherein the wave generated by the at least one sound wave generator is an ultrasound wave, and wherein the ultrasound wave, after being output from the acoustic meta-structure body, is converted to an audible frequency band when hitting an audience or an object near the audience.
10. The display apparatus of claim 2 , wherein the plurality of meta-units comprise meta-units having different structures with different coil shapes configured to shape the traveling path of the wave generated by the at least one sound wave generator.
11. The display apparatus of claim 10 , wherein each of the plurality of meta-units has a structure comprising a graded index distribution gradually varying from a center part of the meta-structure body to an edge of the meta-structure body.
12. The display apparatus of claim 11 , wherein the at least one sound wave generator is disposed outside of the acoustic meta-structure body.
13. The display apparatus of claim 11 , wherein the wave generated by the at least one sound wave generator is an ultrasound wave, and wherein the ultrasound wave, after being output from the acoustic meta-structure body, is converted to an audible frequency band when hitting an audience or an object near the audience.
14. The display apparatus of claim 1 , further comprising: a location tracking sensor that senses a location of an audience, wherein the central control unit receives audience location information from the location tracking sensor.
15. The display apparatus of claim 14 , further comprising: a speaker control unit that receives the audience location information from the central control unit and adjusts directivity of the acoustic meta-structure body.
16. The display apparatus of claim 1 , wherein the directive display unit comprises: an illumination unit that provides light for forming an image; a display panel that modulates the light from the illumination unit according to image information; and a variable optical device that forms directivity of an image formed by the display panel.
17. The display apparatus of claim 16 , further comprising: a display control unit that drives pixels of the display panel by space multiplexing a plurality of pieces of the image information.
18. The display apparatus of claim 16 , further comprising: a display control unit that drives pixels of the display panel by time multiplexing a plurality of pieces of the image information.
