I have had a Lexus Ct200 Sport from new (March 2016).
I have covered 5000 miles in that time.
Yesterday though was the first long trip at fairly high speeds.
Two hours in a whistling noise started from the rear centre of the car which got louder and louder over the next 30 minutes.
It sounded like a coke can had been pierced with the contents spraying out.
If I slowed the noise got less and went completely when I stopped.
I checked the boot and rear of the car with no indications of anything amiss, there was also no indication on any of the monitored systems.
We got back to the car 30 minutes later and drove 60 miles with no further noise.
Lexus had no idea what is was but car will be going in next week.
My only idea was it was some noise from the batteries and it seemed to come from that area.
Anyone with any clues - thanks