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Fulfilling the blessing through hearing the blessing from another person:
One may even initially fulfill the blessing through hearing it from the Chazzan of the Minyan, even if he knows how to say the blessing himself. In such a case, one is to count the Sefira immediately after hearing the blessing of the Chazzan. [This however only applies if the person counting had in mind to include the listener in the fulfillment of the blessing, as well as that also the listener had in mind to fulfill the blessing through the hearing. If however, either the Chazzan or listener did not have in mind to be Yotzei/Motzie, then it is questionable if he has fulfilled his obligation of the blessing. Practically, in such a case he is to make an interval of speech, or enter another room, prior to counting the Sefira and then say the blessing and count.]
May one fulfill the blessing through hearing another person reciting it if a Minyan is not present?
Yes. There is no requirement to have a Minyan present in order to be Yotzei a blessing with another person. Nonetheless, when a Minyan is not present, it is better for each person to say their own blessing rather than be Yotzei with another person.
Is the congregation to be Yotzei their blessing with the blessing of the Chazzan, or are they to recite their own blessing individually?
Whenever a Minyan of people are fulfilling a Mitzvah at the same time, and each individual is performing their own Mitzvah, they can choose to either have one person say the blessing for them all, or have each person recite their own blessing. There is no Halachic precedence for one way over the other, as each method contains an advantageous aspect. Nonetheless, the widespread custom today is for every individual to recite the blessing himself, even if a Minyan is present, and so is the proper directive. When a Minyan is not present, it is always better for each person to say their own blessing rather than be Yotzei with another person, as explained previously.
 Admur ibid; M”A 489:10
 Admur ibid that this is allowed specifically in a Minyan, hence implying that if a Minyan is not present [ten Jews] then one should not rely on another person’s blessing. Vetzaruch Iyun as in M”A ibid, as well as 8:11 no mention is made of that this is limited to the presence of a Minyan. Likewise, in Admur 59:4 he rules that a Yachid may be Motzi a Yachid by Birchas Hamitzvos, Vetzaruch Iyun!
 The reason: As when there are ten Jews doing a Mitzvah together it is allowed for one Jew to say the blessing on behalf of all the congregants, as explained in 8:11. [Admur ibid] See Q&A that this means that only if there is a Minyan is there no preference to saying the blessing on one’s own rather than being Yotzei with another, while if there is less than a Minyan, then it is preferable to say the blessing on one’s own.
 As stated by Admur ibid in the ruling of the 1st opinion.
 See next Halacha!
 Admur 59:4 “An individual may not be Motzi another individual with a blessing with exception to Birchas Hanehenin and Birchas Hamitzvos. And the like of all other blessings, however by Birchas Shema and Birchas Hashevach, a Minyan is required”; Admur 8:11 “If a few people are wearing the Tallis simultaneously, each one says their own blessing each person is to say the blessing on his own, although if they want, they can choose to have one person say the blessing, and the remainder will listen and answer Amen.” 213:6 regarding if a Minyan is not present by Megillah reading, it is still better for one person to read and say the blessing on behalf of all; M”A ibid and Admur 8:11 and 213:6 never conditions being Yotzei with someone on a Minyan being present
The ruling in Admur here 489:1: Admur 489:1 writes that one may be Yotzei with the blessing of the Chazzan being that “As when there are ten Jews doing a Mitzvah together one Jew is able:allowed to say the blessing on behalf of all the congregants, as explained in 8:11.” This implies that if a Minyan is not present [ten Jews] then one may not be Yotzei, or is not allowed to be Yotzei, with another person’s blessing. This clearly contradicts the notion established in all the other sources in Admur and Poskim that a Minyan is never a prerequisite to being Yotzei a Mitzvah or blessing. To note that in M”A ibid, as well as 8:11 no mention is made of that this is limited to the presence of a Minyan. In truth however, one can explain as follows: Admur here in 489:1 never intended to say that a Minyan is required in order to be Yotzei. Rather the intention is to say that in order for it to be initially allowed to be Yotzei with another rather than say it on one’s own, one needs a Minyan present, as otherwise there is not as much of a Berov Am, and the advantage of increasing in necessary blessings overrides the advantage of Berov Am of less than a Minyan. Only when there is a Minyan do we say the advantage of Berov Am is equal to the advantage of increasing in necessary blessings, and hence there is no precedence to one over the other. [See Admur 213:6 for a discussion of the advantage of Berov Am versus the advantage of increasing in necessary blessings] On this Admur ibid intended to say that when there is a Minyan one can choose to be Yotzei with the Chazzan, as if there isn’t a Minyan it is better to say it oneself. See more sources for this distinction in next footnote.
 Admur 489:1 as explained in previous footnote; M”A 213:7 and Tosefta Brachos 6:20 “Ten people who are doing a Mitzvah together”, implying that less than ten does not contain Berov Am; This can also be implied from Admur 8:11 and Michaber 8:5 who rules “If a few people are wearing the Tallis simultaneously, each one says their own blessing each person is to say the blessing on his own, although if they want, they can choose to have one person say the blessing, and the remainder will listen and answer Amen.”, now from the fact that Admur:Michaber plainly stated that each one should say the blessing on their own implies that it is preferable.
 Admur 213:6; One interpretation of Tosefta Brachos 6:20; Or Zarua R”H 262; Mahram Merothnberg 7; Abudarham Seder Tefilos Shel Chol 3; So rule regarding Tzitzis: Admur 8:11; Michaber 8:5; Orchos Chaim Tzitzis 25; See M”A 213:7
 The advantage of fulfilling the blessing through one person is “Berov Am Hadras Melech”, (while the advantage of saying their own individual blessing is to personally say the blessing rather than be Yotzei through a messenger, and thus increase in blessings.) [See Admur 213:6]
 Admur 619:8 regarding Shehechiyanu, Birchas Hallel and Lulav “Although it is proper to be Yotzei with the Chazzan due to Berov Am, nevertheless today …. every person should recite the blessing himself”; M”A 619:3; Chayeh Adam 5:17; M”B 8:13 that so is custom; Piskeiy Teshuvos 213:2
The reason: As in majority of instances the Chazzan does not have in mind to be Motzi the congregation. Admur ibid; Chayeh Adam ibid; M”B ibid]