In the new Continental GT Speed, running at a steady 50mph with the engine off, the meter fluctuated around 61.7dBA – but then rose to only around 62.2dBA with the engine running.
It’s as confounding to read it again now as it was to observe it first hand, because your ears aren’t lying to you.
You can hear the instant the engine starts and easily perceive the difference it makes to the cabin’s ambient noise level, even when it’s only bumbling along just above idle – and then you look down at a meter that might as well be shrugging its shoulders and saying ‘meh’, like some uninterested adolescent.
The Continental GT Speed is a modern luxury car of particularly high standards for mechanical noise isolation, needless to say. In the average PHEV, we could probably expect a greater disparity.
Nevertheless, in any car moving along at a 50mph cruising speed, the greatest individual source of detectable cabin noise usually isn’t the engine, even when there is one fitted. Road noise and wind noise are already more prominent.
And here are some numbers to prove it. The Mercedes-Benz EQS is an exceptionally quiet car, for example, generating just 58dBA of cabin noise at 50mph, but that will have a lot more to do with the fact that it’s a £130,000 luxury Mercedes than simply an electric car.
