Aside from being a mitzvah in and of itself, listening to the communal Torah reading is an expression of honor for the Torah. When one honors the Torah in this manner, the Torah arouses mercy for him and for all the members of his household on both the spiritual and material planes. Accordingly, one should be fastidious not to speak during the communal Torah reading. ~ R’ Sholom DovBer Schneerson of Lubavitch