We can't actually pronounce hieroglyphics. We can sort of pronounce them, but there are significant challenges to what we're able to do. Egyptian's written language had no vowels until Coptic, which leads to two problems. The first is that, obviously, there were vowels in the language. We do not know precisely where they were and we do not know their values. In some words, particularly names and places, we can get a good guess by comparing Coptic and Greek. In most words, however, we just put an "e" in between consonants--so this sign, one of the most common triliterals, is transliterated "nfr" and read as if it said "nefer," even though those are not necessarily the vowels that were actually in the word. This leads us to our second problem. Take, for example, the Egyptian word for house, "hwt." That "w" there is pronounced when we read it as a vowel (the word sounds kinda like "hoot"). It is not a vowel. The uniliteral sign there would be the quail chick, which is transliterated as "w"--but it is not a vowel. Egyptian didn't write vowels, remember? Problem is, we don't really know precisely how that sign was pronounced because the sound evolved and was different in Coptic, from which we get many of our pronunciations for signs. Comparison of similar sounds in related languages like Arabic can help give us an idea of what this was, but we're not totally sure. So when working with Egyptian we pronounce it as a vowel. Another example is the so-called "Alef vulture," the first uniliteral sign. This is transliterated as 3 and usually pronounced as if it were a long "a." In fact it was in Middle Egyptian probably usually either silent or a glottal stop, and in Old Egyptian may have had a different value altogether (I don't know much about that, that's real linguistics, and what I know about the pronunciation of Egyptian is from learning it, not linguistic study). What we pronounce as a "y" is what's called "Yod"--it's written either as a pair of reeds or as a simplified two strokes, and it's transliterated as "y." We have no clue what its value in Old Egyptian was, but in Middle Egyptian it probably had a value like the one we give it--trouble is, there's another sign, transliterated ı͗, that can also have that same sound. This sign's value is pretty mysterious, some people think that when it appears at the beginnings of words it's a stand-in for an initial vowel (of any kind) and it's not clear how it was different from yod when it came in the middle or end of words--we pronounce it like the vowel "i" or as consonantal "y" depending on where it is. Yet another example is ayin, ʾ. We read this, again, as a vowel, short "a"--it wasn't, like all these letters it was a consonant, and its value is highly theoretical. Most of the clearer consonants are pretty well-established by comparison to Coptic, but these consonants that dropped out or evolved into vowels only have theoretical values. The pronunciations of Egyptian that Egyptologists work with aren't really accurate and nobody pretends that they were--in Stargate when they speak in Egyptian we in fact would have no clue how accurate what is being said is, even if we know that the syntax is correct