Less than a year old, not sure of the model, possibly a Scenic. I have looked into this and the reversing sounds have been designed by Jean Michel Jarre for the Scenic, as standard there is a low level hum. If the car was making a hum then I never heard it, understandable when there is other traffic noise.
By contrast, my neighbour has a hybrid Toyota and that sounds damn awful in reverse, like an electric drill where the speed is adjustable on the trigger but at the slowest possible speed, far worse than a Scalextric.