What is that god awful groan and vibration heard and felt when sitting in first class especially 1F. Its fairly consistent with higher airspeeds and usually diminishes during lower angles of attack. The ERJ145 has similar airframe vibrations during cruise but nothing like the 170. Sounds like N1 vibrations and or an access panel open causing rough airflow over the fuselage. Sounds like some impending failure. Spooky.