Still further back are the velar stops . The back of your tongue stops the air at the back of your hard palate. The voiced velar stop is the initial consonant of gill . The unvoiced velar stop is the initial consonant of kill . The glottal stop is unvoiced in English.
Fricatives involve letting the air slide through a narrow opening in the mouth.
They can be prolonged for some time. The air is not completely blocked. The voiced labiodental fricative is the initial consonant of veer . The unvoiced labiodental fricative is the initial consonant of fear . If you make that opening with your tongue against your top teeth, you produce a dental fricative .