Acoustic device and headrest

1. An acoustic device comprising:

a speaker unit; and

a three-dimensional knitted fabric,

wherein the three-dimensional knitted fabric is provided at a position substantially facing the speaker unit while being given tension in a surface direction, and an output sound of the speaker unit is converted to an acoustic wave of a surface sound source by vibration of yarns constituting a pair of ground knitted fabrics constituting the three-dimensional knitted fabric and by vibration of a connecting yarn extending back and forth between the ground knitted fabrics, and the acoustic wave is propagated to an outside,

wherein a plate-shaped bead foam having a predetermined area is combined with the three-dimensional knitted fabric, the three-dimensional knitted fabric is disposed in a tense state so as to correspond to a hole portion formed at a position of the bead foam, the position substantially facing the speaker unit, and the bead foam, the hole portion, and the three-dimensional knitted fabric serve as a resonance part which vibrates air inside the hole portion to make the output sound of the speaker unit resonate.

2. The acoustic device according to claim 1 , wherein the three-dimensional knitted fabric is disposed in a tense state so as to be elongated in the surface direction by a 20% extent or less.

3. The acoustic device according to claim 1 , wherein a non-propagating part not allowing the acoustic wave of the surface sound source to propagate is formed in the three-dimensional knitted fabric.

4. The acoustic device according to claim 3 , wherein the non-propagating part is formed by a process of bringing the pair of ground knitted fabrics constituting the three-dimensional knitted fabric into proximity to each other.

5. The acoustic device according to claim 1 , wherein the three-dimensional knitted fabric also has a function as a cushioning layer that elastically supports a portion of a human body, and is used as part of a body support means.

6. The acoustic device according to claim 5 , wherein the body support means is a seat or bedding, and the three-dimensional knitted fabric is used as part of the cushioning layer constituting the seat or the bedding.

7. The acoustic device according to claim 6 , wherein, in the seat, the three-dimensional knitted fabric is used in part of the headrest.

8. A headrest in which the acoustic device according to claim 1 is incorporated.

9. The headrest according to claim 8 , wherein the three-dimensional knitted fabric also has a function as a cushioning layer that elastically supports a head.

10. The acoustic device according to claim 1 , wherein the plate-shaped bead foam includes a flat surface portion shaped as a flat board.

11. The acoustic device according to claim 10 , wherein the plate-shaped bead foam includes side surface portions between which the front surface portion is located.

12. An acoustic device comprising:

a speaker unit; and

a three-dimensional knitted fabric including a front surface portion and side surface portions between which the front surface portion is located;

wherein the three-dimensional knitted fabric is provided at a position substantially facing the speaker unit while being given tension in a surface direction, and an output sound of the speaker unit is converted to an acoustic wave of a surface sound source by vibration of yarns constituting a pair of ground knitted fabrics constituting the three-dimensional knitted fabric and by vibration of a connecting yarn extending back and forth between the ground knitted fabrics, and the acoustic wave is propagated to an outside,

wherein a plate-shaped bead foam having a predetermined area is combined with the three-dimensional knitted fabric, the three-dimensional knitted fabric is disposed in a tense state, the speaker unit is positioned to substantially face a hole portion of the bead foam and at least one of the side surface portions, and a vibration of the at least one of the side surface portions due to the output sound of the speaker unit is propagated to the front surface portion.

13. An acoustic device comprising:

a speaker unit; and

a three-dimensional knitted fabric,

wherein the three-dimensional knitted fabric is provided at a position substantially facing the speaker unit while being given tension in a surface direction, and an output sound of the speaker unit is converted to an acoustic wave of a surface sound source by vibration of yarns constituting a pair of ground knitted fabrics constituting the three-dimensional knitted fabric and by vibration of a connecting yarn extending back and forth between the ground knitted fabrics, and the acoustic wave is propagated to an outside,

wherein at least one of: fabrics including a knitted fabric, a woven fabric, and a non-woven fabric that are two dimensional or three dimensional; synthetic leather; genuine leather; a synthetic resin film; and a bead foam is combined with the three-dimensional knitted fabric, and

wherein a plate-shaped bead foam having a predetermined area is combined with the three-dimensional knitted fabric, the three-dimensional knitted fabric is disposed in a tense state so as to correspond to a hole portion formed at a position of the bead foam, the position substantially facing the speaker unit, and the bead foam, the hole portion, and the three-dimensional knitted fabric serve as a resonance part which vibrates air inside the hole portion to make the output sound of the speaker unit resonate.