when saying Vayechlu on friday night. Can it be said with someone who just listens due to shemaya keona? LISTENING IS LIKE ANSWERING.
No, for this purpose both must speak the words. The reason for this is that the idea of saying vayechulu together with others — according to those authorities who require this — is that it should be akin to giving testimony.
Testimony requires that both witnesses should testify, and one cannot testify just by hearing the other.
Were this not the case, one could fulfill the saying of vayechulu at Kiddush, because of the people listening.
For the question of whether vayechulu must be said with others or not, see Yerushalayim Be-Mo’adeha (p. 164), who brings a number of opinions, and see also Shut Avnei Levi, no. 15.