Please excuse my digression in to a Hebrew grammar lecture.
In Hebrew, there are 6* letters which have different pronunciation, depending on whether or not there is a dagesh in the letter. Modern Hebrew speakers normally only differentiate between 2 of these 6 letters.
* Sefer Yetzirah lists 7 letters, adding the Reish.These letters are:
- ב - Bet
- ג - Gimel
- ד - Dalet
- כ - Kaf
- פ - Peh
- ת - Taf
If we analyze these letters, they are really 3 pairs of letters. In each pair there is a vocalized and unvocalized letter.
The pairs are:
- ב - פ - Bet and Peh
- ד - ת - Dalet and Taf
- ג - כ - Gimel and Kaf
That is to say that there is little to no difference in these letters when whispering them, when they are unvocalized.
This parallel should also hold true for the forms without dagesh. Indeed this is the case.
- ב - פ - Vet and Feh - This is common usage of these letters in Israeli Hebrew today.
- ד - ת - Dalet here is a "th" as in "the", Taf is t as in "thanks" - This is the common use among Jews from Teiman.
- ג - כ - Gimel here sounds like a French "r", which is the vocalized version of a khaf sound, though more gentle than the way most people pronounce a khaf.
I believe this analysis is logically sound, and shows the following:
- How Kriat Shema should be done correctly in order to lengthen the dalet of Echad.
- A Taf without a dagesh cannot be an "s" sound.
- A Reish is not similar to a French "r"