It is a sound that lies between the two liquids in English. The words "flesh" and "fresh" sound the same t0 the ear that doesn't hear them.

By way of http://ell.stackexchange.com/questions/112384/do-all-native-...

> However, even before their first birthdays, babies begin to lose the ability to hear the distinctions among phonemes in languages other than their own.

From http://www.encyclopedia.com/media/encyclopedias-almanacs-tra...