What dummy entity type to use for looping sound?

[Earendel]

As part of this mod: viewtopic.php?f=93&t=38475
I am increasing a driverless vehicle's speed.

I need the engine sound to continue while the vehicle is moving even though there is no driver.

I think the best way to do this is to have a dummy entity that is playing a looping sound and just destroy it when the player gets in or the vehicle stops. The question is, what prototype type to use?

I can't think of anything suitable.

[Earendel]

I tried a lamp and a boiler but those both had serious issues. In the end I managed to get it working with "fire".