Front and Rear Wind Deflectors

[CPN]

6 hours ago, maclink said:

Do these wind deflectors decrease cabin noise while driving at higher speeds (70mph)?  I'm thinking of getting a set for my Yaris Cross.

That's not really the purpose of wind deflectors. They are really designed to allow you to have the windows "ajar" for extra ventilation, as needed, while smoothing out the airflow over the gap so that a) they are less noisy than it would be with the windows "ajar" without them; and b) it facilitates having the window "ajar" in the rain without the rain coming into the car inside.

There is also a certain extraction effect when the window is down a little with wind deflectors on so that, for example, you can quickly get rid of diesel fumes that may have entered the car via other means (and you weren't quick enough hitting the "Recirculate" button!) once you are on the move again... (e.g. the normal intakes when you are standing in a queue behind a particularly dirty smoky diesel car! Can you tell I hate diesels?! 😉)

To directly answer your question though, I have used my car (a Mk4 Yaris) with and without deflectors and there is very little increase in cabin noise with them on and the windows fully closed compared to them off...