Wind whistle noise coming from front speaker cover during speeds above 80km/h

I fixed mine with weatherstripping meant for a house. That noise was driving me crazy!

 

I actually fixed mine by filling all the voids and gaps with "Greatstuff" behind the speaker. I had whistling on both sides going down the highway and now my Prius is so so so quiet on the highway. So nice.

 

Its the seals on the outer mirror. Like weather stripping on your home door, it becomes too compressed over time and is unable to maintain an airtight seal, allowing the outside elements to enter (air, water).

Take a look at the attached pictures of the factory mirror.
Old broken OEM mirror, the seals are FLAT.


New OEM mirror, the seals are thick (approx. 1/4inch). Should have taken a side view to capture the thickness.


Get some black rubberized weatherstrip at your local big box home improvement store.
Something like this from Lowe's will work ($4.18): https://www.lowes.com/pd/Frost-King-10-ft-x-3-8-in-Black-Rubber-Foam-Window-Weatherstrip/3062421

The "tape like" seals covering the screws, on the bottom, could possibly add to some wind noise, albeit slightly. My money is on the majority of wind noise entering the passenger cabin is due to the flattened outside door mirror seals.

 

Wind noise had been a problem on the driver's side of my 2007. Prior to finding this thread I replaced the tape covering the screw holes at the bottom of the mirror, no change. I spent $50 to replace the rubber seal that runs around the door, but that did nothing. Then I found this thread and applied one layer of electrician's tape as suggested by the OP, and that was sufficient to get rid of the noise.

 

Thanks for your post - how did you remove the speakers? I'm having trouble finding anything online!