One can be yotzei a beracha by hearing it only if it is made by a person who is obligated in the mitzva.[2] Even in order to answer amen, he must hear the beracha from a person whose beracha is meaningful.[3] Therefore, all agree that one is not yotzei and does not answer amen to a beracha that he hears on a recording, as no one is actually reciting the beracha at that time.
Almost all poskim agree that one cannot fulfill the mitzva of hearing shofar via a microphone, telephone, or radio, because one must hear the authentic sound of a shofar.[4] While most poskim likewise disqualify Megilla reading via a microphone, this point is not as clear, since the authenticity of the sound required for shofar is likely unique. Furthermore, even though the Megilla must be heard from a person who is obligated in the mitzva, which would seem to disqualify device-generated reproductions, it is possible to argue that one does hear a person via a microphone. First of all, the ba’al korei, by means of his voice, is directly causing the production of the sound. Moreover, the production is heard at essentially the same time as the ba’al korei is reading. Finally, along with the louder sound of the microphone, the ba’al korei’s voice is also present in the room. Therefore, the lenient position regarding Megilla via a microphone is marginally tenable.[5]
An interesting gemara[6] seems to minimize the importance of hearing the voice of the person reciting, as long as one knows what is being said. The gemara describes a huge amphitheater in Alexandria, in which flags were waved to inform people when to answer amen. This implies that one does not have to hear what is being said in order to answer; he need only know what is being said. This source has limited applicability because, as Tosafot[7] explains, the participants were not attempting to fulfill any mitzva at the time. However, it does seem to indicate that one can at least answer amen without having heard the voice of the person reciting the beracha.
Rav S.Z. Auerbach[8] permits those who hear berachot in shul via a microphone to answer amen, but he rules that one who hears berachot via a radio or a telephone may not. The distinction is based on the fact that the people in Alexandria were close enough to be “connected” to the root of the berachot, even though they were not actually hearing them. In contrast, there is no physical connection between the person reciting and those “listening” at a distance via telecommunication.
It is possible to raise the following counter-argument to Rav Auerbach’s claim (which itself is based on logic, not sources). Regarding answering amen, it is not the authenticity of the voice that is crucial, but rather the connection between that which was recited and the one who “heard” it. Therefore, it is logical that the immediate and realistic reproduction created by live telecommunication creates a palpable connection even over great distances. Although to be yotzei through someone else’s beracha, it is likely that one must hear the original sound emanating from a valid halachic entity, the lesson learned from Alexandria may also apply to those “connected” through modern technology. Indeed, Rav Ovadia Yosef rules that while one cannot be yotzei a beracha via a telephone, he may answer amen and respond even to prayers that require a minyan.[9]
Another factor that might preclude answering amen is the possibility that the voice travels over an area that is filthy or includes idol worship.[10] However, there are several reasons to be lenient on this issue, in addition to the question of the chances that the “sound” travels over such places. First, it is not clear that we pasken that this is a problem, especially when there are other points of leniency.[11] Also, the disqualification due to passing over problematic places might apply only to sound waves and not to the transmission of electrical signals, which will later be used to recreate the sound.
In conclusion, one cannot fulfill a mitzva that requires hearing something specific via telecommunication. It is unclear, however, whether he can answer amen to berachot heard in this manner. One may rely on ample grounds to do so, considering that the stakes regarding an unwarranted amen are lower than for an unwarranted beracha.[12] We would certainly stop short of saying that he is required to answer amen in these cases.[13]