accordian

Many thanks for the replies. Been on a 150 mile round trip today, mainly motorway. Beginning to suspect it could be road noise related as it did appear to change in intensity over different road surfaces. The sound is similar to the type of noise you get in a saloon car when you have the rear seats folded down. (However, seats not folded down). (I believe the battery pack has a cooling fan. Is this normally audible when driving?).

Recently purchased a used (2013) IS300H. Really enjoying my first Lexus and the IS300H is a pleasure to drive. The car is generally very quiet. However, I am a little concerned about a 'howling' sort of sound coming from the rear of the car. This is most noticeable when travelling above approx 40/50mph. The sound doesn't sound like a tyre noise, diff whine or failed wheel bearing noise. As I haven't driven another IS300H, I'm not sure if this noise is 'standard'. Any advice?