Sound system

1 . A sound system that emits, by using at least four speaker units arranged in a seat of a vehicle, acoustic signals of a reproduction target such that the acoustic signals are not able to be heard or hardly heard outside a first range near a user sitting in the seat, and emits a cancellation sound such that noise cancellation by the cancellation sound for canceling noise arriving at the seat affects only a second range near the user sitting in the seat, wherein

the at least four speaker units are not respectively housed in speaker boxes,

sound waves emitted in a direction opposite to the user are diffracted and propagated towards the user by coming around,

at least two speaker units of the at least four speaker units are arranged on a right side from a center of the seat,

at least two speaker units of the at least four speaker units are arranged on a left side from the center of the seat,

the at least two speaker units arranged on the right side and the at least two speaker units arranged on the left side are arranged to sandwich a head of the user,

a (2R-1)-th speaker unit that is one of the at least two speaker units arranged on the right side is arranged at a position closer to a right ear of the user seated on the seat as compared with a 2R-th speaker unit that is another one of the at least two speaker units arranged on the right side,

a (2L-1)-th speaker unit that is one of the at least two speaker units arranged on the left side is arranged at a position closer to a left ear of the user seated on the seat as compared with a 2L-th speaker unit that is another one of the at least two speaker units arranged on the left side,

the acoustic signals of the reproduction target are emitted from the (2R-1)-th speaker unit and the 2R-th speaker unit to be opposite in phase to each other,

the acoustic signals of the reproduction target are emitted from the (2L-1)-th speaker unit and the 2L-th speaker unit to be opposite in phase to each other, and

the acoustic signals are emitted from the (2R-1)-th speaker unit and the (2L-1)-th speaker unit not to be opposite in phase to each other.

2 . A sound system that emits, by using at least four speaker units arranged in a seat of a vehicle, acoustic signals of a reproduction target such that the acoustic signals are not able to be heard or hardly heard outside a first range near a user sitting in the seat, and emits a cancellation sound such that noise cancellation by the cancellation sound for canceling noise arriving at the seat affects only a second range near the user sitting in the seat, wherein

the at least four speaker units are not housed in speaker boxes,

sound waves emitted in a direction opposite to the user are diffracted and propagated towards the user by coming around,

a (2R-1)-th speaker unit and a 2R-th speaker unit that are two speaker units of the at least four speaker units are arranged on a right side from a center of the seat,

a (2L-1)-th speaker unit and a 2L-th speaker unit that are two speaker units of the at least four speaker units are arranged on a left side from the center of the seat,

the two speaker units arranged on the right side and the two speaker units arranged on the left side are arranged to sandwich a head of the user,

the (2R-1)-th speaker unit emits a (2R-1)-th acoustic signal that is one of the acoustic signals of the reproduction target,

the 2R-th speaker unit emits a 2R-th acoustic signal that is an acoustic signal having a phase opposite to that of the (2R-1)-th acoustic signal,

the (2L-1)-th speaker unit emits a (2L-1)-th acoustic signal that is one of the acoustic signals of the reproduction target,

the 2L-th speaker unit emits a 2L-th acoustic signal that is an acoustic signal having a phase opposite to that of the (2L-1)-th acoustic signal, and

at least either one of:

the (2R-1)-th speaker unit and the (2L-1)-th speaker unit are arranged closer to a right ear and a left ear of the user sitting in the seat than the 2R-th speaker unit and the 2L-th speaker unit, respectively, or

the 2R-th speaker unit and the 2L-th speaker unit are arranged closer to the right ear and the left ear of the user sitting in the seat than the (2R-1)-th speaker unit and the (2L-1)-th speaker unit, respectively.

3 . A sound system that emits, by using 2N speaker units, where N is any integer greater than or equal to 2, acoustic signals of a reproduction target such that the acoustic signals are not able to be heard or hardly heard in a range outside a first range near a user sitting in a seat of a vehicle, and emits a cancellation sound such that noise cancellation by the cancellation sound for canceling noise in a second range near the user does not affect a range outside the second range,

the 2N speaker units are not respectively housed in speaker boxes,

sound waves emitted in a direction opposite to the user are diffracted and propagated towards the user by coming around,

the sound system comprising:

a reproduction device including an n-th reproduction unit that outputs a (2n-1)-th acoustic signal that is one of the acoustic signals of the reproduction target and a 2n-th acoustic signal that is an acoustic signal having a phase opposite to that of the (2n-1)-th acoustic signal, where n=1, . . . , and N; and each n is an integer that satisfies 1≤n≤N; and

a speaker system that is installed at a place close to a head of the user sitting in the seat and includes an n-th speaker unit pair (n=1, . . . , N) including a (2n-1)-th speaker unit that emits the (2n-1)-th acoustic signal and a 2n-th speaker unit that emits the 2n-th acoustic signal, wherein

an R-th speaker unit pair is arranged on a right side from a center of the seat, where R is any integer greater than or equal to 1 and less than or equal to N,

an L-th speaker unit pair is arranged on a left side from the center of the seat, where L is any integer greater than or equal to 1 and less than or equal to N,

the R-th speaker unit pair and the L-th speaker unit pair are arranged to sandwich the head of the user, and

at least either one of:

a (2R-1)-th speaker unit and a (2L-1)-th speaker unit are arranged closer to a right ear and a left ear of the user sitting in the seat than a 2R-th speaker unit and a 2L-th speaker unit, respectively, or

the 2R-th speaker unit and the 2L-th speaker unit are arranged closer to the right ear and the left ear of the user sitting in the seat than the (2R-1)-th speaker unit and the (2L-1)-th speaker unit, respectively.

4 . The sound system according to claim 3 , wherein

the cancellation sound is emitted from the (2R-1)-th speaker unit and the (2L-1)-th speaker unit or the 2R-th speaker unit and the 2L-th speaker unit arranged near the right ear and the left ear of the user sitting in the seat.

5 . The sound system according to any one of claim 1, 2, or 3 , further comprising a member that lengthens a sound path in which sounds emitted in the direction opposite to the user direction come around in the user direction.

6 . The sound system according to any one of claim 1, 2, or 3 , further comprising a sound absorbing material capable of absorbing high-frequency components of sounds emitted in the direction opposite to the user direction.