 Voicing is caused by the vocal cords held close by each other, so that air passing through them makes them vibrate.All normally spoken vowels are voiced, as are all other sonorants except "h", as well as some of the remaining sounds ("b", "d", "g", "v", "z", "zh", "j", and the "th" sound in "this").All the rest are voiceless sounds, with the vocal cords held far enough apart that there is no vibration; however, there is still a certain amount of audible friction, as in the sound "h".