Achumawi has 37 consonants. Most of these form pairs of plain and laryngealized or glottalized series. Plosives and affricates also have a third, aspirated member of the series (except for the single glottal stop) which is contrastive only syllable-initially and probably derives historically from clusters, as in the neighboring and possibly related Yana language.
| Bilabial | Alveolar | Palatal | Velar | Uvular | Glottal | ||
|---|---|---|---|---|---|---|---|
| Stop | plain | p | t | c | k | q | |
| laryngealized | p̓ | t̓ | c̓ | k̓ | q̓ | ʔ | |
| aspirated | pʰ | tʰ | cʰ | kʰ | qʰ | ||
| Fricative | plain | s | x | h | |||
| epiglottal | h̓ | ||||||
| Nasal | plain | m | n | ||||
| glottalized | m̓ | n̓ | |||||
| Approximant | plain | w | l | y | |||
| glottalized | w̓ | l̓ | y̓ | ||||
The laryngealized stops are similar in articulation to the ejective glottalized stops of neighboring languages, but more lenis, that is, not "popped" unless an unusual effort is made at articulating the distinction. The plain-aspirated distinction is neutralized and realized with aspiration or voiceless release in syllable-final position and before another consonant. Plain stops are voiced before a short vowel or after an aspirated stop, voiceless elsewhere.[1]
In a 5-vowel system, consisting of 5 short and long, /ɪ ɛ ʌ ə ʊ/ and /i e a o u/, the mid vowels may be of secondary origin historically, as in Yana and Atsugewi. A schwa [ə] appears epenthetically between the consonants of certain prefixes, as in lhúpta "let's go!". Two degrees of length are contrastive for both vowels and consonants. In downriver dialects, the second mora of a long vowel is devoiced before a plain or aspirated consonant (preaspiration) and laryngealized before a laryngealized consonant. Long vowels are typically more peripheral and short vowels more centralized. In downriver dialects, utterance-final syllables may be devoiced or whispered.[1]
Unlike the neighboring and related language Atsugewi, Achumawi has distinctive tone on every syllable.[1]