See question above. Is it prohibited to answer Amen in such a case?

As we mentioned on question 482 and others, most Poskim maintain that we do not equate an electronically reproduced sound with a natural voice, one who hears a brocho (blessing) by phone, zoom or over a microphone merely knows that it has been recited at that moment, but has not actually heard it. The case is analogous to the Great Synagogue of Alexandria (described in Sukka 51b), which was so large that many congregants could not hear the leader. In order that they would know when to answer “amen,” someone would wave a banner to indicate that the leader had ended a brocho.As is mentioned in Talmud (Suka 51b) in regards to the flag signals of the well attended Great Synagogue of Alexandria, we do answer amen even when we did not hear at all the recited brocho, as long as we are aware which brocho is being recited. Horav Shlomo Miller’s Shlit”a opinion is that under the chupa, where there is a requirement to be yotze with the first two brochos of the Rov, even when the Rov who performs the ceremony is reciting the brochos using a microphone, since he is so close to the Chosson and Kallah and they could hear him clearly anyway, they comply with his blessings, as they do not need the loudspeakers at all. Minchas Shlomo (1:9) writes that one should not answer Amen to a brocho heard on the phone, and he considers this an Amen Levatolo (a wasted Amen). He explains that in the shul in Alexandria everyone was together in one building, but if one is miles away there is no connection to the person who recited the brocho, therefore amen cannot be said. Horav Eliashiv zt’l (quoted in Avnei Yoshfeh 1: 9) equates hearing a brocho over a telephone or radio to receiving a telegram that someone will recite a brocho at a certain time. Just as we would never think of reciting amen in such situation, so, too, a zoomer is removed from the brocho recitation and he should not answer Amen. HoRav Moshe Shternbuch Shlit’a (Teshuvos Vehanhagos 1: 155) similarly rules that one should answer “amen” only when close enough to at least hear the natural voices of other people answering amen to the brocho, but not when hearing it from extremely far away. Indeed it seems that there is indeed a prohibition of answering Amen in vain as when it is not required.