Proto-Norse phonology

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 (as with any language), the overall system of phonemes and their distribution remained largely unchanged.

Consonants

 * 1)  assimilated to a following velar consonant. It was  before a plain velar, and probably  before a labial-velar consonant.
 * 2) Unlike its Proto-Germanic ancestor, the phoneme  was probably no longer a fricative. 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 , ,.
 * 1) The exact realisation of the phoneme  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. Traditionally, ʀ (a small uppercase R) has been used to represent this sound in early Norse inscriptions.

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.


 * 1)  had developed from  through a-mutation. It also occurred word-finally as a result of the shortening of Proto-Germanic.
 * 2) The long nasal vowels,  and  occurred only before . Their presence was still noted in the 12th century First Grammatical Treatise.
 * 3) 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.
 * 4) The back vowels probably had central or front allophones when  or  followed, as a result of i-mutation:
 * 5) * >,  >  (later , )
 * 6) * >  (later  or )
 * 7) * 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.
 * 8) Towards the end of the Proto-Norse period, stressed  underwent breaking, becoming a rising diphthong.
 * 9) Also towards the end of the Proto-Norse period, u-mutation began to take effect, which created rounded allophones of unrounded vowels.
 * 1) Also towards the end of the Proto-Norse period, u-mutation began to take effect, which created rounded allophones of unrounded vowels.

Diphthongs
At least the following diphthongs were present:, , ,.


 * 1)  was later rounded to  due to u-mutation.
 * 2)  eventually underwent breaking to become the triphthong . This was preserved in Old Gutnish, but simplified to a long rising  or  in other areas.
 * 3) As  occurred exclusively in environments with i-mutation, its realisation was probably fronted . This then developed further into, which then became.

Accent
Old Norse had a stress accent which fell on the first syllable. 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 didn't appear until the Old Norse period.