I agree with Franky. I listen to music in the car so quietness is important. I measured all the cars I test drove with a decibel-o-meter app on the phone. The ST level was 85dB during normal driving. That was the same as our Lexus and quieter than the Vette and my truck. (A VW salesman said when the GTI is in sport mode a microphone picks up engine compartment noise and pipes it into the cab - NOT!)
Anyway I took a five hour trip in the ST and found it to be reasonable, even at highway speeds.
When you said ST I thought Ford LOL. I had to double check the forum I was on