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.