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next or adjoining room
隣室から笑い声が聞こえた。
Laughter could be heard from the next room.
隣室とは薄い壁一枚で隔てられている。
The next room is separated only by a thin wall.
大事な話は隣室に聞こえないように声を潜めた。
I lowered my voice so the important conversation wouldn't carry to the next room.