Note that this is just a theory based on personal observations. We can’t back up our claims on visual typing with any studies or statistics as of the moment. So consider this article more as something written for fun.
The Eight Intelligences

• Existential intelligence (Ni) is driven by slow buildup and breakdown of enthusiasm. It makes you overall more visionary, more deliberate, more purposeful in your speech and your actions.
• Interpretative intelligence (Ne) is driven by quick buildup and breakdown of enthusiasm. It makes you overall more curious, better at spotting hidden things, better at grasping and reading the room.
• Performative intelligence (Fe) is driven by more quickly warming up to and trusting other people, but also more difficulty dealing with breeches in trust. Makes it easier to be yourself around others and to express yourself.
• Artistic intelligence (Fi) is driven by needing more time to warm up and trust other people. They are overall more intimate once they warm up to a person. More private with their personal world.
• Analytical intelligence (Ti) is driven by more slowly feeling positive about ones own work and performance. Overall more self-critical, but also holds self to higher standards. Can be lazy, taking shortcuts when possible. Constantly customizing and fine-tuning one’s own work to be more accurate.
• Practical intelligence (Te) is driven by more quickly feeling good about one’s own work and performance at a task. More straightforward, direct, and rough. Estimates and tries to be swift in completing tasks. Overall more productive types.
• Natural intelligence (Se) is driven by more quickly feeling pleased and in touch with their surroundings, but can be more impulsive and lack self-control. More awake and ready for action. Good at judging taste, touch, smells.
• Structural intelligence (Si) is driven by more slowly feeling pleased and calm in an environment, but maintain calm for a longer time. Makes you more watchful and careful, more detailed, studious, and better at spotting issues.

General Voice Rules

• The dominant function rules. For example the Fi emotiveness spikes doesn’t overtake the enthusiastic tone.
• Louder speech is lead by extroverted functions.
• Silent speech is lead by introverted functions.
• Ni can be more excited than Ne but takes longer to buildup. Ne can be less excited than Ni once initial interest has faded.
• Se keeps itself awake by increasing it’s voice tone in between every word.
• When Fe drops, Ti takes over. When Te drops, Fi takes over. Unenthusiastic Ne sounds like Si.
• IXXP restrain articulation. Speech can sound like a slow and controlled action.
• EXXJ can’t hold back articulation. Can struggle to slow down speech, take fewer breaks.
• IXXJ has an overall slow but unrestrained voice.
• EXXP has a generally quick but restrained voice.

Example voice tones in N and S

It usually takes a longer time to know where a Ni-type is going. A Ne type takes you through each step in their thought process.
Every voice has a quality or vibe
Because we have all learnt to notice these differences, we’ve learnt to associate them with personality. Someone with strong extroverted thinking may be perceived as more aggressive and direct. An introverted intuitive is often questioned for having hidden motives – their voice always sounds like it’s going somewhere. An extroverted feeler is perceived as more warm, passionate and animated.
An extroverted intuitive sounds more curious and invites people to share more. An introverted feeler appears more authentic, ethereal, personal. An introverted thinker appears more dispassionate and logical. An extroverted sensor has more stage presence and is good at keeping their listeners attention. An introverted sensor appears more trustworthy – a good quality of a politician.
Recommended reading on visual typing
http://www.neojungianacademy.org/2016/08/11/visual-typing/
http://www.neojungianacademy.org/2016/09/07/every-types-favourite-gesture/