Proto-Norse phonology probably did not differ substantially from that of Proto-Germanic. Although the phonetic realisation of several phonemes had probably changed over time, the overall system of phonemes and their distribution remained largely unchanged.
Consonants • assimilated to a following velar consonant. It was before a plain velar, and probably before a labial-velar consonant. • Unlike its Proto-Germanic ancestor , the phoneme probably no longer had a velar place of articulation. It eventually disappeared except word-initially. • , and were allophones of , and , and occurred in most word-medial positions. Plosives appeared when the consonants were lengthened (
geminated), and also after a nasal consonant. Word-finally, , and were devoiced and merged with , , . • The exact realisation of the phoneme , traditionally written as
ʀ in transcriptions of runic Norse (not to be confused with the phonetic symbol used in other languages), is unclear. While it was a simple alveolar sibilant in Proto-Germanic (as in Gothic), it eventually underwent
rhotacization and merged with towards the end of the runic period. It may have been pronounced as or , tending towards a
trill in the later period. The sound was still written with its own letter in runic Old East Norse around the end of the first millennium.
Vowels The system of vowels differed somewhat more from that of Proto-Germanic than the consonants. Earlier had been lowered to , and unstressed and had developed into and . Shortening of word-final vowels had eliminated the Proto-Germanic overlong vowels. • had developed from through
a-mutation. It also occurred word-finally as a result of the shortening of Proto-Germanic . • The long nasal vowels , and occurred only before . Their presence was noted in the 12th-century
First Grammatical Treatise, and they survive in modern
Elfdalian. • All other nasal vowels occurred only word-finally, although it is unclear whether they had retained their nasality in Proto-Norse or had already merged with the oral vowels. The vowels and were contrastive, however, as the former eventually developed into (triggering
u-mutation) while the latter was lowered to . • The back vowels probably had central or front allophones when or followed, as a result of
i-mutation: • > , > • > , > (later , ) • > (later or ) • did not originally occur before or , but it was later introduced by analogy (as can be seen on the Gallehus horns). Its allophone was probably , later . • Towards the end of the Proto-Norse period, stressed underwent
breaking, becoming a rising diphthong . • Also towards the end of the Proto-Norse period,
u-mutation began to take effect, which created rounded allophones of unrounded vowels.
Accent Old Norse had a
stress accent which fell on the first syllable, like its ancestor,
Proto-Germanic. Several scholars have proposed that Proto-Norse also had a separate
pitch accent, which was inherited from
Proto-Indo-European and has evolved into the
tonal accents of modern
Swedish and
Norwegian, which in turn have evolved into the
stød of modern
Danish. Another recently advanced theory is that each Proto-Norse long syllable and every other short syllable received stress, marked by pitch, eventually leading to the development of the Swedish and Norwegian tonal accent distinction. Finally, quite a number of linguists have assumed that even the first phonetic rudiments of the distinction did not appear until the
Old Norse period. ==Attestations==