Voicelessness

Voiceless
◌̥
Encoding
Entity (decimal)	̥
Unicode (hex)	U+0325

In linguistics, voicelessness is the property of sounds being pronounced without the larynx vibrating. Phonologically, it is a type of phonation, which contrasts with other states of the larynx, but some object that the word phonation implies voicing and that voicelessness is the lack of phonation.

The International Phonetic Alphabet has distinct letters for many voiceless and modally voiced pairs of consonants (the obstruents), such as [p b], [t d], [k ɡ], [q ɢ], [f v], and [s z]. Also, there are diacritics for voicelessness, U+0325  ̥ COMBINING RING BELOW and U+030A  ̊ COMBINING RING ABOVE, which is used for letters with a descender. Diacritics are typically used with letters for prototypically voiced sounds, such as vowels and sonorant consonants: [ḁ], [l̥], [ŋ̊].

Sonorants are sounds such as vowels and nasals that are voiced in most of the world's languages. However, in some languages sonorants may be voiceless, usually allophonically. For example, the Japanese word sukiyaki is pronounced [su̥kijaki] and may sound like [skijaki] to an English speaker, but the lips can be seen to compress for the [u̥]. Something similar happens in English words like peculiar [pʰə̥ˈkj̊uːliɚ] and potato [pʰə̥ˈtʰeɪtoʊ].

...
Wikipedia