The key is in the labels:
These are slack-voiced consonants, an uncommon sort of phonation similar to breathy voice. The vocal cords vibrate, but they're also opened to let more air through.
The trick with the IPA is that it's not as precise as laypeople tend to think. Many languages have two types of stop consonants distinguished by voice onset time (the time from the release of the closure to the start of vocal cord vibration), so the IPA provides symbols for those two types; some languages even have three, so it provides a third symbol as well (d t tʰ
). But those symbols only have meaning in contrast to each other; the IPA doesn't define exactly what range of voice onset times each symbol represents.
So if you need more than those distinctions, what can you do? Well, you can add some diacritics; "voiced t
" and "voiceless d
" (t̬ d̥
) seem like they should just be the same as normal d
and t
, but remember, the meaning of these symbols is only really defined in relation to each other. So those are reasonable (and not uncommon) ways to represent "something that's kind of like a voiced consonant and kind of like a voiceless consonant", which don't require creating entirely new non-IPA symbols.