I hear low pitched humming/whistling noise from the front right side of my '06 ES330. The noise is something like what you hear when you blow air into a big plastic bottle. The pitch doesn't change. It's always low and not so loud, but it's there. What could it be?
Noises are very difficult to diagnose without actually hearing them. Humming/whistling noises can come from the action of the tire tread on the pavement; wheel bearings; CV joints; differential bearings; accessory drives like the power steering pump, alternator, AC compressor, belt tensioner, & pulleys; from electric fans; and wind noise. Since a 2006 car is likely under warranty, my recommendation is to go back to the dealership and go on a road test with someone from the service department so that they can hear the noise you are concerned about.
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