I know when my next-door neighbor wakes up, because I can hear the creaking sound of the door as he/she opens it in the morning.
ご質問ありがとうございます。
"I know when my next-door neighbor wakes up,"=「隣人がいつ起きたか私には分かる」
"because I can hear the creaking sound of the door as he/she opens it in the morning."=「なぜかというと、彼・彼女が朝、ドアを開けるときのキーという音が聞こえるから。」
ご参考になると幸いです。
I know when my next door neighbours wake up because their door always creaks when they open it in the morning.
I always know when my neighbours have woken up in the morning because their door makes a squeaky sound.
to creak「きしる・キーと音を出す」を使って言うと、次のように言えます。
ーI know when my next door neighbours wake up because their door always creaks when they open it in the morning.
「隣の人が起きるとわかる。なぜなら朝彼らがドアを開けるといつもキーという音が鳴るから」
to make a squeaky sound「キーという音を立てる」を使っても言えますよ。
ーI always know when my neighbours have woken up in the morning because their door makes a squeaky sound.
「朝隣の人が起きるといつもわかる。なぜならドアがキーという音を立てるから」
ご参考まで!