There are no specific restrictions on the types of obstruent sequences that can occur.

This would have been more likely if h₃ was a voiced velar obstruent to begin with.

Consonants There are two series of obstruent consonant.

But v does not trigger voicing of preceding obstruent, nor is it devoiced.

In obstruent clusters, retrograde voicing assimilation occurs, even across word boundaries:

Mucus obstruent, cleaning with low suction.

It is voiceless and aspirated [k'] before an obstruent or open juncture.

Obstruent voicing/devoicing as in Russian and Czech.

The reflexes of a series of obstruent consonants, described as "tense" or "geminate".

Russian-style obstruent voicing/devoicing does not occur.

The original strong grade was preserved in hais-ta "to stink" because of the preceding obstruent s which prevented gradation.

In the past participle th (also t after d) is silent but makes a voiced obstruent voiceless:

The "voiced/voiceless" obstruent pairs of Ojibwe vary in their realization depending on the dialect.

The glottal stop occurs only adjacent to a vowel, and, within words, it does not follow any obstruent except (the prefix) /s/.

The Germanic spirant law, similarly, affected combinations of an obstruent followed by -t-.

"Obstruent harmony and tonogenesis in Jabêm."

In a cluster of consonants ending in an obstruent, all obstruents change their voicing according to the last one of the sequence.

It depends on whether the initial consonant is a sonorant or obstruent, as in yang-tone splits in other Chinese dialects.

Devoicing of voiced obstruent codas (e.g., characterize may be realized with a final [s])

Light syllables (syllables with short vowels and optionally also obstruent codas), do not have the two-way contrast of heavy syllables.

The d is omitted if the root ends with an obstruent or nasal consonant: dut 'two', dut.

In Semitic studies, they are commonly transcribed using the convention of placing a dot under the closest plain obstruent consonant in the Latin alphabet.

Short vowels before voiceless stops (or sonorant + voiceless obstruent) are also front, but non-velar items cannot undergo front-raising.

Also, Catalan has final obstruent devoicing, thus featuring many couplets like amic "(male friend") vs. amiga ("female friend").

In Semitic linguistics, an emphatic consonant is an obstruent consonant which originally contrasted with series of both voiced and voiceless obstruents.