:Devoicing:

Partial or total loss of vocal fold vibration for a speech sound. For example, in English voiced obstruent sounds are usually devoiced when adjacent to voiceless sounds or to silence. For instance, the initial and final sounds of the word dog, when it is uttered in isolation, have little or no vocal fold vibration.

Devoicing is represented by a combining ring diacritic below (U+0325), or for symbols with a descender with a combing ring above (U+030A) as in d̥ɒɡ̊.