So I was translating a song (full lyrics here: 反芻の印象) and there is an onomatopoeia in the middle which I don't understand. It's らん. It repeats multiple times (you can hear it in the song on Youtube, 【初音ミク】反芻の印象【オリジナル曲】, at 1:00) and I don't know what it's trying to mimic. I can't find what it could mean anywhere, and I don't know what it could be besides that. The song is about trains, so I'm assuming the sound effect is related to that, but really I have no idea what it's supposed to sound like, even after listening to it over and over.
Additionally, the line after that in the song is:
(I tore it up and avoided it?) which I'm quite sure is a pun, which is why I'm hesitant to translate it as written, especially since it doesn't really make contextual sense. (As the next lyric is 鈍行列車 点いて 消える きまぐれ信号, the slow train lights up (the night) and then vanishes, a whimsical signal - that makes sense together, but not with 裂けて 避けた.) Is this just a weird line, or is there some meaning to these words, especially put together, that I'm not seeing?
Thank you for your help!