Ok. When driving at moderate speed 30-40mph. I hear a faint strange noise. It almost sound like someone trying to start a car in the distance but don't turn over.

I can only hear this when driving along a road where there is a continuous "island" barrier separating on coming traffic. I figure the sound is reflecting off the island barrier. If there is not island I don't seem to hear it.

I don't hear anything driving 25mph in my neighborhood.

It could be just the wind whistling on something. I took off the roof rack.

Any ideas what it could be? Any ideas what I can check.

thanks

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Silver Honda Accord, 2006
Silver G500, 2003
Silver SLK-320, 2002
Black ML-320, 2000
Bule Porsche 993 Targa , 1997
Silver Merkur XR4Ti, 1987