Go Back   EcoModder Forum > EcoModding > Aerodynamics
Register Now
 Register Now

Reply  Post New Thread
Submit Tools LinkBack Thread Tools
Old 10-14-2011, 08:51 AM   #1 (permalink)
EcoModding Lurker
Join Date: Jul 2011
Location: canada
Posts: 1
Thanks: 0
Thanked 0 Times in 0 Posts
booming-wind noise

I have been interested in air flow considerations for quite some time.

SITUATION: Many recent cars develop considerable booming/air pressure variations(large vortex generation?) when the rear side windows are down.
I own a Honda fit 2008
OBjECTIVE: reduce the considerable wind noise and booming when rear wind is open
SOLUTIONS examined:
solution #1. "A" pillar window slightly open-
Result : no booming but loud wind noise.
solution # 2. Fitted a vertical deflector 30cm X8cm at 45 degrees at front edge of open rear window-
Result: much less booming but loud wind noise.
solution # 3. Purchased Honda MUGEN grooved wind visors ( waiting for delivery) which promises of less wind noise /less booming
Result: not known yet

Below : a photogragh of the Honda after a drive in a snow storm.

REQUEST, with regards to booming AND wind noise:
#1. Explain the observed deposited snow , in air flow terms (or by drawing it directly on photo on my Honda FIT '08
#2. Relate experience with HONDA MUGEN GROOVED side window wind deflector

  Reply With Quote
Alt Today
Popular topics

Other popular topics in this forum...

Old 10-14-2011, 12:16 PM   #2 (permalink)
PSmodder lurker
Join Date: Jan 2009
Location: Chino
Posts: 1,568
Thanks: 24
Thanked 861 Times in 496 Posts
Try blowing the top edge of a bottle and hear the low & loud sound it creates. Helmholtz resonance is happening. The moving volume of air is going over that small opening of the rear window and starts an oscillation with the inside volume of air, the corresponding frequencies creates a Helmholtz resonance & painful eardrums. Helmholtz Resonance
  Reply With Quote
The Following User Says Thank You to botsapper For This Useful Post:
aerohead (10-15-2011)
Old 10-14-2011, 12:41 PM   #3 (permalink)
Master EcoModder
NeilBlanchard's Avatar
Join Date: May 2008
Location: Maynard, MA Eaarth
Posts: 7,873

Mica Blue - '05 Scion xA RS 2.0
Team Toyota
90 day: 42.48 mpg (US)

Forest - '15 Nissan Leaf S
Team Nissan
90 day: 156.46 mpg (US)

Number 7 - '15 VW e-Golf SEL
90 day: 155.81 mpg (US)
Thanks: 3,386
Thanked 2,883 Times in 1,812 Posts
Open both rear windows at once and see if it still happens? On my xA, I have to limit the rear windows to an inch or two down, to avoid this -- and opening them a lot will add drag anyway. The noise is very annoying, but what are you gonna' do?
Sincerely, Neil

  Reply With Quote
Old 10-14-2011, 02:23 PM   #4 (permalink)
EcoModding Lurker
Rick Rae's Avatar
Join Date: Aug 2011
Location: Surry, VA
Posts: 47

The CARDIS - '07 Nissan Versa S HB
Team Nissan
90 day: 30.9 mpg (US)
Thanks: 6
Thanked 7 Times in 4 Posts
I can create almost an "air hammer" effect in the CARDIS. Very powerful, very low frequency (maybe subsonic - you almost feel it more than hear it), a few hertz repetition rate. It happens if the back windows are rolled down, the front windows are rolled up, and speed is in the 40s or better. (No, I don't drive that way -- discovered it by accident one day after being parked with all four windows down and forgetting to roll the rear windows up.)

But here's the thing: I never experienced it before I replaced the rear seats with a load floor (and I' ve forgotten the rear windows were down more than once).

I agree it's likely a resonant cavity issue, and my experience hints that INTERIOR changes might also help you. Try some expanded foam or fluffy blankets in the back seat. Not a solution, but it may give you clues to help solve the problem.

Me, I figure it'll come in handy if someone I don't want riding with me insists on "shotgun." Five minutes tops and they'll be begging me to let them out at the next corner.

Let us know what you find out, please; I'm curious.


  Reply With Quote
Reply  Post New Thread

Thread Tools

Powered by vBulletin® Version 3.8.11
Copyright ©2000 - 2020, vBulletin Solutions Inc.
Content Relevant URLs by vBSEO 3.5.2
All content copyright EcoModder.com