Why is there an 'ear' component in the character for smell? 闻 聞
「聞」(Baxter-Sagart OC: /*mu[n]/) is comprised of semantic「耳」(ear) and phonetic「門」(/*mˤə[r]/), indicating the meaning to hear. For example,「新聞」means news (literally meaning new information passed on by hearing/reading/etc.)


  「門」does not play a meaning role in「聞」. For that matter, it does not play a meaning role in「問」, either.


To smell is a semantic extension. For example, in English, there's something fishy going on is used to describe a situation which is not quite right, literally referring to the smell of fish, but metaphorically referring to someone picking up information about their surroundings and deducing that something feels off.