|Plosive||p b||t d||k ɡ||kʷ ɡʷ|
|Fricative||ɸ (β)||θ (ð)||s z||x (ɣ)||xʷ|
- [ŋ] was an allophone of /n/ before velar obstruents.
- [ŋʷ] was an allophone of /n/ before labial-velar obstruents.
- [β], [ð] and [ɣ] were allophones of /b/, /d/ and /ɡ/ in certain positions (see below).
- The phoneme written as f was certainly still realised as a bilabial fricative (/ɸ/) in Proto-Germanic. This can be deduced from the fact that in Gothic, word-final b devoices to f, and also from Old Norse spellings such as aptr [ɑɸtr], where the letter p rather than the more usual f was used to denote the bilabial realisation before /t/.
Proto-Germanic had four short vowels  five or six long vowels, and at least one "overlong" or "trimoric" vowel. The exact phonetic quality of the vowels is uncertain.
- /e/ could not occur in unstressed syllables except before /r/, where it may have been lowered to /ɑ/ already in late Proto-Germanic times.
- All nasal vowels except /ɑ̃ː/ and /ũː/ occurred word-finally. The long nasal vowels /ɑ̃ː/, /ĩː/ and /ũː/ occurred before /x/, and derived from earlier short vowels followed by /nx/.
PIE ə a o merged into PGmc a; PIE ā ō merged into PGmc ō. At the time of the merger, the vowels probably were [ɑ] and [ɑː], or perhaps [ɒ] and [ɒː]. Their timbres then differentiated by raising (and perhaps rounding) the long vowel to [ɔː] . It is known that the raising of ā to ō can not have occurred earlier than the earliest contact between Proto-Germanic speakers and the Romans. This can be verified by the fact that Latin Rōmānī later emerges in Gothic as Rumoneis (that is, Rūmōnīs). It is explained by Ringe that at the time of borrowing, the vowel matching closest in sound to Latin ā was a Proto-Germanic ā-like vowel (which later became ō). And since Proto-Germanic therefore lacked a mid(-high) back vowel, the closest equivalent of Latin ō was Proto-Germanic ū: Rōmānī > *Rūmānīz > *Rūmōnīz > Gothic Rumoneis.
A new ā was formed following the shift from ā to ō when intervocalic /j/ was lost in -aja- sequences. It was a rare phoneme, and occurred only in a handful of words, the most notable being the verbs of the third weak class. The agent noun suffix *-ārijaz (Modern English -er) was likely borrowed from Latin around or shortly after this time.
The following diphthongs are known to have existed in Proto-Germanic:
- Short: /ɑu/, /ɑi/, /eu/, /iu/
- Long: /ɔːu/, /ɔːi/, (possibly /ɛːu/, /ɛːi/)
Note the change /e/ > /i/ before /i/ or /j/ in the same or following syllable. This removed /ei/ (which became /iː/) but created /iu/ from earlier /eu/.
- Cet article comporte des éléments adaptés ou copiés de l’article de Wikipédia en anglais : , sous licence .
- On i and e see Cercignani (1979.