How to make HVAC vents quiet?

[foghorn67]

It might be nice to have an AC at full blast in your preferred vehicle without the woosh of the noise while the fan speed is cranked up.
I know larger fans on the blower motors might make the fan quieter, but what about the sound as it rushes through ducts and out the vents?
Is that possible? Would any kind of acoustic engineering help with this?
On the blower motors, my old Mustang has a cylinder shaped fan. Kind of like those big dryers people use to dry off a flooded room. Do they use these in modern cars, or are they propeller shaped?

 

[Minerva]

Too much air volume makes the noise level go up. Undersized ductwork causes this. If you need quiet and more air you must use larger ductwork.

Those blowers are calle squirrel cages. Funny thing as I've never seen a squirrel in one.

 

[foghorn67]

Originally posted by: Minerva
Too much air volume makes the noise level go up. Undersized ductwork causes this. If you need quiet and more air you must use larger ductwork.

Those blowers are calle squirrel cages. Funny thing as I've never seen a squirrel in one.

haha, that's funny. I knew there was a name for it, but haven't heard it until now.
So if you had larger vents, would it be ideal to cool off a car's interior in the summer?
Would it lessen the effect of air being directed in the face or wherever people like to angle the vents?

 

[Minerva]

Well in a car it would look funny with 8" vents. The bassheads would double them as for vents in their boomboxes.

Older cars had much more room behind the dash so the ductwork was much simpler. Today's cars have ducts that look like a brass instrument so no wonder they woosh. Although a good engineer can get the noise manageable with heads up designing and testing. ALGOR sims help a lot here.

 

[foghorn67]

Originally posted by: Minerva
Well in a car it would look funny with 8" vents. The bassheads would double them as for vents in their boomboxes.

Older cars had much more room behind the dash so the ductwork was much simpler. Today's cars have ducts that look like a brass instrument so no wonder they woosh. Although a good engineer can get the noise manageable with heads up designing and testing. ALGOR sims help a lot here.

Okay. Bare (Bear?) with me here. So, on today's dashes with limited room, and even less room behind the dash...how could they engineer that if one would want to? Carefully shaped ducts? Any kind of lining in the ducts? Any kind of textered pattern that could help?

 

[Minerva]

Originally posted by: foghorn67

Originally posted by: Minerva
Well in a car it would look funny with 8" vents. The bassheads would double them as for vents in their boomboxes.

Older cars had much more room behind the dash so the ductwork was much simpler. Today's cars have ducts that look like a brass instrument so no wonder they woosh. Although a good engineer can get the noise manageable with heads up designing and testing. ALGOR sims help a lot here.

Okay. Bare (Bear?) with me here. So, on today's dashes with limited room, and even less room behind the dash...how could they engineer that if one would want to? Carefully shaped ducts? Any kind of lining in the ducts? Any kind of textered pattern that could help?

Yes that's the ticket. With injection moulded plastic (RIM) they can texture the surface or add nipples(!) etc. to quiet things down. R & D costs money. This is why a Kia screams like a kangaroo with its sack caught in a seesaw and a Mercedes barely hums at WOT.