The Wind Noise Condition

The first step of the repair process in correcting a windnoise condition is to identify the cause(s) of the noise.

Gain a thorough understanding of the circumstances under which the noise was created. A determination must be made as to whether the cause of the noise is air escaping from the vehicle or outside air turbulence.

A. Questions Specific To All Windnoise Conditions

To assist in diagnosing and repairing the owner's vehicle quickly, the following information should be obtained:

1. What specific noise is objectionable?

a. Whistle?
b. Flutter?
c. Rush of Air?
2. Under what condition does the noise occur?

a. In motion?
b. Heater/AC blower motor on or off?

3. Does the noise appear to be...

a. Air leaving the body?
b. Air passing over the body's exterior surface?

4. In which occupant seating position of the vehicle is the noise most objectionable?

a. Front Seat b. Rear Seat

1. Driver's seat? 1. Left passenger's seat?
2. Center passenger's seat? 2. Center passenger's seat?
3. Right passenger's seat 3. Right passenger's seat?

5. At what speed does the specific noise first occur?

a. Less than 10 miles per hour?
b. 10-34 miles per hour?
c. 35-55 miles per hour?
d. Over 55 miles per hour?

6. In what general area does the noise appear to originate?

a. Front of Vehicle b. Sides of Vehicle

1. Grille 1. Windshield Pillar
2. Bumper 2. Upper
3. Hood 3. Center
4. Fender 4. Lower
5. Shroud (Cowl) area
6. Windshield

c. Rear of Vehicle

1. Rear Window
2. Tulip Panel
3. Tailgate/Window (Wagons)
4. Quarters
5. Rear Bumper
6. Roof Rack (Wagons)

FIGURE 1:

B. Analyzing Windnoise

When a vehicle is in motion, it strikes the air causing it to bend around the vehicle and deflect around the windshield pillars (Figure 1). When this occurs, areas of high and low pressure are then created. It is the difference between the pressure build up that varies levels of sound pitches. As air strikes the base of the windshield, it backs up. This causes a low pressure center to develop outside the vehicle around the front pillars and side windows. The amount of low pressure build up along the sides of the vehicle is increased by the impact speed of the air as it strikes against the windshield surface. The faster the vehicle is traveling, the greater the pressure difference becomes.
This pressure buildup at the windshield causes the air flow that is filtered through the vehicle vents and/or air conditioner to build up high pressure inside of the passenger compartment. The faster the vehicle is traveling, the greater the inside pressure becomes. The speed of the vent fan will also have an effect on pressurization of the passenger compartment.

The pressure pushes outward on the glass and other seals. This situation is not normally a problem, but if a door or window is out of alignment, leaks can develop and cause a wind whistle.

The high inside pressure and low outside pressure is separated only by vehicle's sheet metal panels, glass, weatherstrips and body seals.

When an opening is created at a joint at any of these areas, the high inside air pressure will move toward the low outside pressure area to create an air leak.

The shape of the opening would then determine if an audible noise or whistle can be heard. It may require a specific vehicle to create enough high pressure to break the seal.

The vehicle has a large area, plus a number of exterior attachments in which air must move around. As a result, some rush of air will be heard and is considered normal.

FIGURE 2:

Examples are:

1. Door Alignment-A door should fit properly into the Vehicles body opening for several reasons:

a. Appearance
b. Ease of operation
c. Smooth quiet air flow.

A vehicle door that is not properly aligned will act similar to an air scoop. The inside area of the door jamb will become pressurized and create air turbulence which may be transmitted as noise inside of the passengers compartment (Figure 2).

2. Outside Sports Mirrors-They are shaped similar to a bullet in front, and flat across the face or rear.

FIGURE 3:

When a vehicle is moving, its outside mirrors strike and bend the air around it. This flow of air around the body of the mirror can create a low pressure area or vacuum across its face, allowing turbulence to build up (Figure 3).
Because of the styling design of the sports mirror, the noise cannot be eliminated.

The noise source can be verified by taping over the face of the mirror and then subject vehicle to the same road conditions.

The high pressure inside air moves toward the low pressure (vacuum) area through the door belt sealing strips and/or any other voids in the mirror head or inside the door. If the air passage is shaped just right, an objectionable air noise can be heard. Thus, you could have a wind whistle and wind roar condition.

FIGURE 4:

3. Areas and Percentages of Reported Objectionable Windnoise (Figure 4).

It is estimated that 7% of all reported objectionable windnoise conditions can be located at the front end (bumpers, grill, hood and fenders) of the vehicle.

Another 90% of the reported objectionable windnoise conditions are located in the area between the dash panel and the rear edge of the door or center pillar.

The remaining 3% of those reported conditions were located between the rear edge of the door or center pillar area to the rear of the vehicle (usually vent window seals, luggage racks or tailgates and wind deflectors).

FIGURE 5:

4. Classifications of Windnoise: It is important to note that wind will not create a noise until it is forced to change direction, or is forced to move around an object.

Windnoise Categories, (Figure 5) may be classified into the following: