To purchase this Sefer, click here
Does one answer Amen after hearing someone recite the blessing of Al Divrei Torah?
One who hears another person reciting Birchas Hatorah is to answer amen after each of the three blessings, including after the first blessing of Al Divreiy Torah, prior to Veharev Nah.
 47/5; This follows the second opinion mentioned in 47/5, the accepted custom and ruling of the Mekubalim, that the first blessing is considered to be a separate blessing from Viharev Nah. [brought in Admur 47/5 and so concludes Ketzos Hashulchan 5/8; Siddur of Rav Raskin footnote 136; Rav Akiva Eiger; Daas Torah 47/6; Aruch Hashulchan 47/13
Other opinions mentioned by Admur: See Background brought in previous Halacha for the dissenting opinion which does not consider Viharev Nah a blessing of its own and hence in their opinion one is not to answer Amen until the conclusion of Viharev Nah.
Other Opinions: There are Poskim who rule that due to the above dispute the blessing of Al Divreiy Torah is to be said quietly, without allowing others to hear, in order to avoid controversy. [M”B 47/12] The M”B ibid writes that majority of Achronim rule one is not to answer Amen.