Such sounds are often referred to informally as lenis or half-voiced in the case of consonants.
In some Chinese varieties, such as Wu, and in a few Austronesian languages, the 'intermediate' phonation of slack stops confuses listeners of languages without these distinctions, so that different transcription systems may use ⟨p⟩ or ⟨b⟩ for the same consonant.
In Xhosa, slack-voiced consonants have usually been transcribed as breathy voice.
[1] Wu Chinese "muddy" consonants are slack voice word-initially, the primary effect of which is a slightly breathy quality of the following vowel.
[1] Javanese contrasts slack and stiff voiced bilabial, dental, retroflex, and velar stops.