Droning noise from rear

[40t]

2008 V70. Slight (irregular) droning noise from the rear at motorway speeds, but only when there's a rear passenger on board. Not emanating from the passenger. But seems to be coming from the same (nearside) corner as the passenger.

The year before last there was an MOT advisory - trailing arm bush deteriorated, but not excessive. Though I'd imagine that wouldn't produce this sort of noise?

Only 71k, though very crashy over potholes. I understand that this wasn't this model's best feature, even when new, but have been thinking about replacing the shocks (with Sachs?), despite the low mileage, on the basis that they've been compressed by a heavy vehicle for 11 years now.

Any thoughts gratefully received.