"Who is heard?"
I'm not sure what you mean.
Are you referring to the fact that πώς, πού take accents in Greek even though they are one syllable?
That is to distinguish them from πως, που which have other meanings.
But τι is usually not written with an accent (probably because the homophonous τι = because, short for γιατί, is poetic), nor is ποιος, which has no word that it could be confused with at all.