Engine Noise

[Demonicon]

So when I'm idling you hear the normal engine hum....then all of a sudden......it's like a vibration and the engine gets a bit louder......then it's back to the normal hum........then the vibration and the deeper louder sound...etc..etc. Is this normal?

 

[Senecahighlander]

My wife's Sonic is loud like that all the time. I'm trying to find out if it's normal or not. It seems like there's very little insulation or sound reduction with how loud it is, and there seems to be a lot of vibration going on as well.

Is this just a "Sonic" thing?