Phonology according to Benedict and Matisoff

The phonology of Proto-Tibeto-Burman here is from James Matisoff's 2003 reconstruction, much of which is based on Paul K. Benedict's earlier reconstructions.

Consonants
Proto-Tibetan–Burman has at least 23 consonants (Matisoff 2003:15). Some descendants of Proto-Tibetan–Burman, especially the Qiangic languages, have developed dozens of sibilant fricatives and affricates.

Proto-Tibeto-Burman also has many final nasals, stops, and liquids.

Vowels
Proto-Tibeto-Burman vowels can be split into primary and secondary sets. Modern-day Tibeto-Burman languages have anywhere from five vowels (Written Tibetan and Jingpho) to dozens of monophthongs and diphthongs (Loloish and Qiangic languages) (Matisoff 2003:157). Matisoff (2003) also notes that languages which have greatly simplified or eliminated final consonants tend to have more vowels. The open front unrounded vowel *a is by far the most common and stable vowel in Tibeto-Burman languages.

Matisoff (2003) reinterprets diphthongs from Paul Benedict's reconstruction as long vowels.

Preservation of stops
Sino-Tibetan languages go through a series of four stages in which final stops and nasals gradually decay (Matisoff 2003:238-239).
 * 1) The six final stops and nasals, *-p, *-t, *-k, *-m, *-n, *-ŋ, are all intact. Written Tibetan, Lepcha, Kanauri, Garo, and Cantonese are currently in this stage.
 * 2) One or more final consonants have been reduced or dropped. In Jingpho and Nung, the velars (*-k) are replaced by glottal stops (-ʔ), while in other languages they are completely dropped. In Mandarin Chinese, all final stops are dropped, and *-m has merged with *-n.
 * 3) All finals stops become glottal stops or constrictions (such as creaky voices), and final nasals may be replaced by nasality in the preceding consonant. Languages currently in this stage include modern Burmese and Lahu.
 * 4) There are no glottal or nasal traces of former final consonants left in the syllables.