I came up with this question when looking through the answer for this question, which states that a convergent duct(obstruction) compresses the exhaust so that its pressure matches the ambient pressure. In the comments section another question was answered like this:

Q:Doesn't the pressure decrease and the air accelerate when the diameter decreases ?

A:The pressure decrease happens in the obstruction and after it - it's increased by the obstruction, between the fan and the nozzle exit.

I am a bit confused by what's meant by "pressure decrease in the obstruction" and "pressure increased by the obstruction". What really is the effect of converging the duct, increase exhaust speed to decrease static pressure or compressing exhaust to increase pressure?

I came up with this question when looking through the answer for this question, which states that a convergent duct(obstruction) compresses the exhaust so that its pressure matches the ambient pressure. In the comments section another question was answered like this:

Q:Doesn't the pressure decrease and the air accelerate when the diameter decreases ?

A:The pressure decrease happens in the obstruction and after it - it's increased by the obstruction, between the fan and the nozzle exit.

I am a bit confused by what's meant by "pressure decrease in the obstruction" and "pressure increased by the obstruction". What really is the effect of converging the duct, increase exhaust speed to decrease static pressure or compressing exhaust to increase static pressure?