> How certain is it that the H2 and H3 laryngeals were pronouced
> [x] and [xw]?
Not very certain at all! There's been some discussion of this on the
list - a hunt through the archives might be profitable. In brief (as far
as I understand it!) the facts are:
(a) It's clear that the laryngeals stood in sonority between resonants and
obstruents (a resonant becomes vocalised in preference to a laryngeal, but a
laryngeal can become vocalised between consonants)
(b) The guess that they were fricatives of some kind therefore seems
plausible, and is widely accepted.
(c) Because they both colour an adjacent vowel to a back vowel, they are
thought to be fricatives at the back of the mouth, but how far back is
anyone's guess. (In Classical
Hebrew, which also has fricatives that colour vowels, the fricative [x] does
not colour them, but the fricatives further back do.)
(d) The theory that H3 was rounded is due to the fact that it colours an
adjacent vowel to a rounded vowel. Some people also guess it was voiced,
but this is based purely on a single word (bibo / pibati etc to drink).
So really, we don't know!
Peter