18.104.22.168 r => [r] (rolling r as in Spanish in words like pero), [ʀ] (r as in French in words like rue (street) and r very similar to h as in health
22.214.171.124.1 [r] (rolling r as in Spanish or Italian)
There are two different realisations of the r and none of them exists in English. Furthermore the rolling r is famous for being difficult to produce irrespective of the mother tongue, because it exists only in few languages.
The [r], the rolling r of Spanish / Italian, is produced by putting the tip of the tongue loosely at the upper incisors. To be precise: At the gum of the upper incisors. If we do that and breath, the air flow will press the tongue down. That way we will obviously not produce any sound. Now we can make the tongue a little bit harder, for the beginning so hard, that we stow air behind the tongue and that way we will not produce any sound either. However in between these two positions there is a position where the force produced by the air stream and the force of the tongue are more or less equal and the tongue starts fluttering. You have more or less the same effect you have with a flag. There is one force, the gravity, that press the flag down and another force, the wind, that lifted it. That's why a flag flutters. Below a little exercise that may be helpful. This [r] rolling r sounds very different than the gutturale r [ʀ], that is produced with a vibration of the uvula.
example (rolling r like in Spanish or Italian)
example (guturale r like in german or French)
falar (to speak) , barco (shipf)
rua (street) , honra (honour)
The rolling r is in general the more difficult one. How difficult it is depends from the position of the tongue, in other words from the sound that has been produced before. The most easy starting point is the t or the d, because in this case the point of the tongue is already at the right position, the gum of the upper incisors. Lets start with an easy word, to drink for instance. Here you have the german version, trinken, but that doesn't make any differrence, try to say drrrrrrrrrrrink with a rolling r.
In the case of to drink the point of the tongue is already in the right position. (d and t are produced at the same point.) The only difference between t / d and r is that in case of the t / d we stow air behind the tongue and let it out suddenly. In the case of the rolling r we have a flow of air that makes the tongue flutter. However flutter means that there is one force that pushes towards a basic position and another force that pushes against this basic position and these two forces have to be more or less equal. The forces that pushes toward the basic position is the tension of the tongue and the force that pushes against this basic position is the air flow.
The rest is like driving a car. (At least if you don't drive an automatic car.) The more you accelerate, the more you have to push the clutch, otherwise you will stall the engine, and the less you accelerate, the less you have to push the clutch. If you put a lot of tension on your tongue, you have to breath strongly to press the tongue and you won't produce any sound. If you put only a weak tension on your tongue, you won't produce any sound either. You have to have a certain frequency to produce a sound. Try it out and you will end up producing a lot of following r. That's the first step. Say drrrrrrrrrrrrrrrrrink. Various r is not bad if you want to learn Spanish, because in Spanish or Italian there are actually two r. In pero (but) it is pronounced only one time, but in perro (dog) it is produced several times. However in Portuguese we have only the single version. If you succeed in producing a lot of following r, try to produce only one. That should be easy if you succeded in producing several of them.
Remark for those who speak Spanish: One could believe that the strong r, where the tongue flutters several times, represented in Spanish by rr corresponds to the Portuguese doble r. Thats not the case. The Portuguese doble r is a gutturale r. The Spanish doble palatale, rolling r doesn't exist in Portuguese.
guttural r as in French or german
rolling r as in Spanish or Italian
What we describe here is an official standard, in other words what you find in grammar books. In practice there is a wide range of realisations of the guttural r. If you don't restrict the flow of air, you get a sound like the Spanish jota in words like járabe (syrup) or even an h. However we have no intention to write a scientific study without any practical value about this issue.
The rolling single r (not the Spanish rr!) as in Spanish is used
at the end of a word (apart from Rio de Janeiro, there it is pronounced guttural)
falar (to speak), mulher (women)
at the the end of syllable (apart from Rio de Janeiro, there it is pronounced guttural)