How to Make Voice and Voiceless Sounds

[fxdung]

Is this correct: to make voiceless sound the glotis more open and more tense; to make voice sound the glotis more narrow and less tense?I don't know how to make the vocal cord vibrate and to make it not vibrate?

 

[jtbell]

What do you do differently between the following pairs of sounds? (first is voiced, second is voiceless)

'b' versus 'p'
'd' versus 't'
'g' versus 'k'
'z' versus 's'

Do any of these pairs both exist in Vietnamese (which is your native language, if I remember correctly)?

 

[Bandersnatch]

The glottis has nothing to do with voicing. At least not in the English language. It's all about the vocal cords.

I don't know how to make the vocal cord vibrate and to make it not vibrate?

In all languages most vowels are voiced. Put your hand on your neck where the larynx is and start pronouncing the vowels you know. Of English, or Vietnamese. Any language really. You will feel vibration in the voice box.
Then say those same vowels, but whispering. Whispering disengages the vocal cords. Your hand will sense a lack of vibration.
You want to control that vibration to contrast the voiced/unvoiced consonants.