How to Heed: Participating in a Brachah
There are certain situations where a person may wish to be yotzei (to meet a halachic obligation) through the recitation of a brachah by another. In fact, with regard to certain mitzvos—such as when hearing the Megillah together—it is halachically preferable for one person to recite the brachah for all, implementing the words of Mishlei: B’rov am hadras Melech (the glory of the King is in the multitude of people).
In order to be yotzei for a mitzvah or birchas hanehenin (brachah on a pleasurable substance) through another’s brachah, the one reciting the brachah must carry at least the level of halachic obligation as the listener. The listener must foremost have kavanah (intent) to fulfill their obligation through the speaker, and the speaker must likewise have kavanah to include them. If either lacked intent, it is halachically questionable whether the listener fulfilled their obligation.
It is also important to hear the recitation of the brachah in full, or at least—as in the case of lengthy brachos—the critical phrases. The listener must hear the natural voice of the one reciting the brachah and not an electronic rendition through a microphone, telephone receiver or a computer speaker.*
The physical environment must be appropriate for the recitation of a brachah—clean, with unsightly or odorous sources properly removed or concealed. Ideally, the listener should answer “Amen”. The listener must refrain from any hefsek (interruption) until they perform the mitzvah or partake of the food, drink or pleasurable item. The phrase “Baruch Hu uvaruch Shemo” (Blessed is He and blessed is His Name—traditionally recited when hearing Hashem’s holy Name) is also considered a hefsek, as would any extraneous words inserted by either the speaker or listener to a brachah.
One of the requirements for being yotzei with another’s birchas hanehenin is a situation of k’vius ([all participants seated in a] fixed position), with the exception of brachos associated with a mitzvah such as Kiddush, Havdalah and the related brachos on spices and fire.
The prevailing custom before partaking of food is to be yotzei another’s brachah only on bread or wine, or foods eaten during a meal, as well as other drinks which are commonly drunk together in a manner of k’vius even outside of a meal. In addition, when participants at a meal would otherwise not recite their own brachah acharonah (blessing after a meal), it is a mitzvah to recite it aloud on their behalf, although in most circumstances, we do not rely on being yotzei a brachah acharonah through another.
*For similar discussions see Halachah #651: Mezuman on a Microphone; Halachah #642 on being yotzei through an electronic device; and Halachah #377 on a communal Tefillas Haderech.