Tosafoth 15a Iy R. Yosi and V'R. Yehuda

In the first of these tosfoths, the relevance of Grace after meals (Birchath Hamazon) to the arguments concerning hearing what one says is discussed. Essentially, the agument is made that :

1. Shema is the paradigm for the (bracha on) giving of Terumah;
2. Therefore these actions have the same auditory requirement as Shema
3. But Birchath Hamzon (BH) is an independant Torah level obligation
4. And BH does not include a stated auditory requirement
5. Therefore BH cannot be used to prove a point about the auditory requirements of Shema, Megillah or (the Bracha on) Teruma.

Tosfoth answers that once the paradigm for (the Rabinnicly decreed) fulfillment of (such) acts had been established to include an audibility requirement, it comes to include BH, even though it has an independent existence.

I think that the next Tosafoth sheds another light on this argument.

The V'R. Yehuda tosafoth discusses the problem of reading the Mishna in Megilla concerning the ability of a minor to fulfill the obligation of the congregation with his reading of the Megillah. Tosafoth first disposes of the idea that the minor is below the age of education based upon an explicit Mishna in Rosh Hashana (29A) which does not allow one not obligated in the Mitzva to act for one obligated. This is possibly a comment on the forthcoming "correction" of this Mishnah on the next page.

Tosafoth then deals with a problem in positing that the minor is of educable age (at least 9 or 10 years old). Quoting the gemarrah further on in Brochoth (20B), we find a case of a boy reciting BH for his father, whose obligation to recite BH is Rabbinic on the basis of the small amount eaten.

Tosafoth resolves the problem in two ways. The first invokes the nature of the Rabbinic obligation to recite BH for a small portion as a extra stringency that can (therefore) be easily fulfilled.

The second (famous) answer involves the nature of the reciter's obligation. In the case of the BH for the father, the only Rabbinic element ( on the part of the reciter) is his age. In the case of the Megillah, the fundamental obligation to recite the Megillah is Rabinnic. In addition, the reciter's "obligation" (actually permission) to recite is Rabbinic. Two Rabinnics are one too many.

However, there may be another level to the juxtaposition of these Tosofoths. The discussion of a Rabbinic basis for (certain) recitations of BH could mean that BH also adheres ( at least under those circumstances) to the auditory rule imposed on Megillah and Terumah based upon the Shema paradigm. And once there is a situation in which the auditory requirement exists, exceptions are discouraged (ab initio) or forbidden (ex post facto).

15a:

On the requirement to hear the Shema:

The (unidentified) first author (tana Kamma) says that one need not hear the Shema to fulfill the obligation of reciting the Shema.

R. Yosi requires that one hear the shema

The (unidentified) first author (tana Kamma) is later presumed to be R. Yehuda.

The meaning of hearing: Shema (hear) is probably more accurately translated as heed. It means more than sound waves impacting on the eardrum. Thus, R. Yosi can derive that it means "heed" or hear AND any language that the listener understands. There is unanimity about the idea that the Shema can (or must) be in a language that the reciter understands.

The gemarrah tries to define the opinions. A Mishnah in Terumoth is brought. The mishna ( the second in trumoth and the end of which defines a deaf person as one who can neither hear nor speak) says that a person who is deaf but can speak should not tithe his crop, but if he didi the tithe is valid. Rashi (presumably based upon the gemarrah that immediatedly follows) says that the problem with the deaf person tihthing is that he cannot hear the bracha (blessing).

There may be another problem, one that, in some ways fits the discussion more easily. The deaf person might not be able to say the viduy masser. Viduy masser is a declarartion of the fulfillment of the tithing obligation. It derives from a verse in Deuteronomy ( 26:12). A mishna in Sota (7:1 or 32A) lists statements that may be made in any language and those that must be made in (the original) Hebrew. Presumably, the deaf person cannot fulfill this Torah level requirement. The inability to hear himself make this declaration would appear to be problem with the tithe of the deaf. This is not brought up in the gemarrah, Rashi or Tosafoth, so it is wrong.