If a person happens to be in the vicinity of a prayer service, and he hears Kaddish, Barechu or Nakdishach, is he required to answer? The Ben Ish Hai (Rav Yosef Haim of Baghdad, 1833-1909) seems to indicate that one who hears these parts of the service is required to respond, even if he is in a different room and not part of the Minyan. By contrast, several other Poskim, including Hacham Bension Abba Shaul (Jerusalem, 1924-1998), maintained that although one is permitted to respond in such a case, this is not obligatory. Rav Shmuel Wosner (1913-2015), in Shebet Ha'levi, writes that if a person is learning Torah near a Minyan, and responding to Kaddish and the other prayers would disrupt his study, then he does not need to respond. Thus, although it is certainly worthwhile to respond to Kaddish, Barechu and Nakdishach, as each response fulfills a Misva and is very significant, this is not obligatory, and one does not need to interrupt his Torah learning for this purpose.