Brochas: Daf Mem Heh amud aleph

R. Shimon ben Pazzi said: "From where is it derived that the translator (of the Torah reading) is not permitted to raise his voice above that of the reader?  For it is stated (Exodus 19:19): 'Moses would speak and G-d would respond to him with a voice'. The words 'with a voice are redundant, so what do they teach: 'with a voice (equal in volume to that) of Moses."

Tosfos points out in the name of the Rif that presumably Moses when translating spoke at the top of his voice so he could be heard by the whole people. Since G-d was speaking only to Moses one might have expected the volume to be different; that it wasn't, shows us that there must be an obligation on the translator to match his volume to that of the reader.

However, the Maharsha suggests that it was Moshe who was reading in Hebrew and that it was G-d who was translating into the 70 languages (see Gemara Shabbos 78b where it says each and every word which issued from the mouth of HKBH split into 70 languages). In consequence, the proof would be that despite the fact that G-d was talking to everyone and Moses only to G-d, HKBH kept His voice at the same lower volume used by Moses.