It is no longer fashionable to use features like [+/- voc] or [+/-
syll] (which used to be manipulated in various ways to define vowels,
glides (semivowels) and liquids). Some r-like sounds qualify as
glides -- the major variants of English /r/ certainly do -- but other
rhotics are definitely consonantal. Some sounds are ambiguous in
terms of class membership. For example, a uvular
fricative/approximant [R] may pattern with true fricatives in some
languages, whereas a sound with the same articulation and the same
acoustic properties will function as a (rhotic) sonorant in other
languages (French, Germn). An alveolar tap between vowels is likewise
interpretable as a rhotic, and therefore a sonorant (e.g. in
Spanish), or as (a brief allophone of) a stop, and therefore an
obstruent (e.g. in English). The point is that the physical
properties of a segment do not always determine its class. One has to
know how the sound in question functions within a given language-
specific phonotactic system.

Piotr



--- In phoNet@y..., "mariano de vierna y carles-tolra" <m.v.ct@t...>
wrote:
>
>
> Piotr and David, thank you for the biblography.
>
> Piotr it is enought for me with just the manual you
mention,
> I have searched it in amazon.com and I think it is what I was
asking for.
>
> Thank you for your explanations and the link you gave,
i have visited
> it and there I have found also the kind of physical explanations of
> the acoustical traits that i wanted to know.
>
> [you wrote]
> "Rhotic" sounds are difficult to define; the class includes several
> types of sound -- trills, flaps, taps, frictionless continuants and
> even fricatives. Most show the lowering of the third formant, but
> some do not. Perhaps the best definition is a negative one: rhotics
> are non-lateral liquids (or segments equivalent to liquids in terms
> of phonotactic functions).
> [mariano]
> Well, i see that there are more questions that need to be answered.
> A problem that i have with rhotics is that I have not yet understood
> why are they +vocalic, because the voiced component -wich is called
also
> svarabatic component- that i think might be the reason to consider
> them +vocalic is not always present, as for example in "ere" when
> the rhotic is not a trill and is in between vocalic phones (?).
>
> Thank you -once more- for the link to the Prat program.
I use
> the "Speech Anylizer" of the SIL (that can be found at
www.sil.org )
> and is a good program, but one thinks that never is enough to know
> what one has if there is something else that one might try, so that
i have
> asked for the Prat also.
>
> Yours cordially,
> mariano