Boruch... Goal Yisroel

In the time of the Rishonim, Omen was said after Go'al Yisro'el both in the night and in the day in Ashkenaz, and the Sephardim held that it was considered Hefsek. Later the Omen was not said in Ashkenaz too (during Shacharis) for this reason, but in any case definitely not by finishing the Brocho quietly, since this is not Kovod for the Brocho (a Brocho is supposed to be said out loud. The way to prevent having to say Omen was by finishing the Brocho together with the Chazzan (the minhag practiced by many people nowadays that the Chazzan doesn't finish Go'al Yisro'el out loud was not accepted by many Lita'i Gdolim - Rav Auerbach and להבדיל בין החיים והחיים Rav Elyashiv are very much opposed to it).

Michael FRBSH