I think there was a post by an audiologist that used a sound level meter to measure this. I think the noise level was ok stock.

I do have a pair of the ER custom ear plugs and they are great!

 

I do windows up on Cali freeways because the concrete whine is usually pretty bad, cross-wind buffeting from trucks can be really bad, and keep some a/c when it it 110. Not a bad thing to do instead of top up.

 

Top down/Windows up is also handy when attempting to carry on a conversation with your passenger, or an important call (using a handsfree headset, of course - pay attention to the road, it's better to ask the caller to repeat than to ask the caller to call 911 b/c you just had/caused an accident)