Fricative vowels

I got this from a non-affiliated conlanger friend of mine:

> In Sweden, they were first noticed in the place called Viby (which I have no
> idea whatsoever of where is). Vibrant/approximant vowels, if I got it
> correctly [...]
> In other words, they were pronounced, I think, like with an r-ish, or z-ish
> sound to them; perhaps simultaneously pronounced with r or z, or perhaps
> just pronounced with a vibrating tongue.
I told him there are also such vowels in Mandarin, IIRC. Can
anybody confirm or correct this? And what about the Sweden vowels?
I think this feature is exclusive of Viby (wherever it is); do you
know of any other places?


--Pablo Flores