For example, the two speakers arranged back-to-back may include a primary speaker and a secondary speaker for forming directivity, a primary speaker for reproducing the left ear signal and a primary speaker for reproducing the right ear signal may be arranged at a predetermined interval in a first direction, a secondary speaker for reproducing the left ear signal may be arranged at the same position as the primary speaker for reproducing the left ear signal in the first direction, and a secondary speaker for reproducing the right ear signal may be arranged at the same position as the primary speaker for reproducing the right ear signal in the first direction.

Alternatively, for example, the two speakers arranged back-to-back may include a primary speaker and a secondary speaker for forming directivity, a primary speaker for reproducing the left ear signal and a primary speaker for reproducing the right ear signal may be arranged at a predetermined interval in a first direction, a secondary speaker for reproducing the left ear signal may be arranged at a position closer to the primary speaker for reproducing the right ear signal than the primary speaker for reproducing the left ear signal in the first direction, and a secondary speaker for reproducing the right ear signal may be arranged at a position closer to the primary speaker for reproducing the left ear signal than the primary speaker for reproducing the right ear signal in the first direction. In this case, for example, the secondary speaker for reproducing the left ear signal and the secondary speaker for reproducing the right ear signal may be the same speaker.