The fronting of back vowels before the segment represented by the rune
algwiz in Old Norse (Runic: kūR
ON: kýr‘cows’) is problematic
because there is no consensus on the phonetic value to be reconstructed for the
conditioner, a reflex of Proto-Germanic+/z/. This study presents an
acoustic experiment testing the fronting effect of codas [z], [ʒ],
and [ɹ] on realizations of the representative back vowel /u/, as
these are possible reconstructed values of algwiz. Based on
observed coarticulation, we argue that a voiced alveolar fricative
[z]—and not postalveolar [ʒ] or rhotic
[ɹ]—is the best reconstruction for the conditioner of
R-umlaut, and that this reflex of PGmc+/z/ in North Germaniccaused
umlaut before rhotacism and merger with PGmc+/r/.