Futuristic engine loop sound effects.

[Skurge]

Hello everyone, I'm seeking if possible royalty free sound effects that loop of futuristic/hover car engines. A variety would be helpful so I can determine what is suitable or just for variety of different noises to avoid repetition.

I'm intending to use these for 3D audio on NPC vehicles.

 

[TheGentlemanLoser]

do you need free to download and royalty free, or just royalty free?