I am starting the arduous journey of studying the japanese language and my first reference has ended up being 'Concerning the Sound of a Train Whistle in the Night'. A character says '夜中の汽笛くらい'. Furigana of 夜中 is given as よなか in the book but Tenjin dictionary example sentences all translate as やちゅう. Is it common to have multiple readings not only for kanji but also for multi kanji 'words'? Upon seeing 夜中 is there a single reading that would spring to mind to at least a vast majority of 日本人. Please help me.