Whistle, Roar, Rush, Wind Noise Information

Fig. 1:

When moving at highway speeds, air pressure inside a vehicle becomes significantly greater than the air pressure outside, as shown in Figure
1. If there's a leak, the escaping air causes a hiss or whistle.

You don't have to look any further than a tire for an example of a similar condition. The air pressure inside the tire is more than the air pressure outside the tire.

Fig. 2:

If the tire is punctured, the high pressure air inside the tire leaks out. A wind whistle is similar to the hiss of a leaky tire. High pressure air inside the car seeps out if all of the seals aren't tight. Refer to Figure 2.

WIND ROAR:

Wind roar is caused by air passing over or through an opening between two body surfaces.

The sound made by blowing across the top of an open bottle is similar to a wind roar. Air flowing across the top is interrupted or redirected by the bottle.

Vehicles are carefully engineered so openings between body surfaces don't interfere with airflow.

Fig. 3:

If body surfaces aren't aligned properly, they can cause wind roar, as shown in Figure 3. You'll want to make adjustments so wind passes over these openings quietly.

WIND RUSH:

Wind rush is usually less irritating than wind roar or whistle.

As a vehicle moves, a cushion of air moves along with it. This cushion does a good job of insulating the inside of a car from the noise caused by air rushing over it.

Fig. 4:

The more aerodynamic a vehicle is, the less air is disrupted, and the smaller the cushion is. Refer to Figure 4.

Most drivers won't notice wind rush, but some do - especially if you've already repaired a whistle or roar condition, and they're listening for wind noise.

You may have done all you can short of changing the shape of the vehicle, and the customer still isn't satisfied. In this case, you or the service advisor may want to explain to the customer what's causing the noise and how you determined the cause.

However, before you tell your customer it's a wind rush problem, you should be confident it's not a whistle or roar that can be repaired.