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2001 Rx300 Weird Effect


jgoodman
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So Im driving from San Diego to LA the other day and accidentally put the back windows all the way down going about 70 on the freeway.

Suddenly this really amazingly weird and very loud low frequency throbbing begins, like there is some harmonic resonance that is making the whole car into some kind of subsonic woofer. I almost lost control, it was so unexpected. I couldnt even figure out what it was at first, but finally when I closed the rear windows it stopped.

I then began experimenting a little..it doesnt happen if both front and rear windows are open, just rear and nothing else. Sunroof must be closed too. It seems to really kick in over 50mph. I guess its some kind of sympathetic vibration caused by the aerodynamics or vaccum of the car when only the back windows are open..????

Just wondering if anyone else has experienced this? or could try it? Im curious if its just my car or what....it doesnt really bother me (unless its shaking things apart) but it was certainly weird.

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IMO, RX300 has a sloped back making it small trunk space compared to Highlander. The sloped back was an aerodynamic design so as to avoid air resistance. When the incoming air slide up the car and come down the rear, it hits the rear top. With sloped rear, the returning air does not hit the rear top of RX300 and make the SUV runs quieter. Don't you realize sedan is always quiet?

Fast moving object always creates a vacuum space on its path. A perfect designed vehical should create a 100% vacuum space. Since no vehical is 100% aerodynamic designed, we won't be 100% suffocated inside the vehical. RX300 probably was so close to aerodynamic designed that you heard that kind of "close to vacuum state" sound when you open the windows at high speed.

When you open the windows at high speed, the higher the better, and sit in the rear, do you feel a lot of wind blows on your face? If it doesn't, you probably get one of the best areodynamic design cars in the world.

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With just the rear window(s) down basically you're setting inside a child's toy whistle.

The effect is referred to as a sonic standing wave.

Both my Ford station wagons had the same effect but luckily I could lower the glass portion of the tailgate slightly and kill the effect.

Basically the wind flowing across the open window acts effectively the same as a child blowing air into a toy whistle, the volume of the whistle determines the frequency and his lung power the volume. Given the enclosed volume of the RX to the rear of the air entry point the frequency will be extremely low and at 70MPH the volume is definitely painful to one's ears.

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My ES does this also, but interestingly my dad's old 98 LS400 never did (same coefficient of drag). Haven't tried it in his new 04 LS.

It is so annoying I agree. I never use the windows not even the sunroof as I hate wind rush (part of why I bought the Lexus) but recently we were on a trip with some family and they sat in the back and liked the windows open. That throbbing is terrible, I found tilting the sunroof was the best way to make it go away.

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