There is one note that can be shared with this and the 500 white noise trophy:
Please note that white noise does not appear on the Gentle difficulty. The further you get into the game and class trials, the more White Noise will appear during the Class Argument settings. To avoid any problems you might have with aiming for the White Noise, it would be better to use the back touchscreen to clear the White Noise. Do not to this if you're planning on also shooting immediately after that, as the cursor will remain wherever you last hit the White Noise. You should be able to normally get this as you progress through the class trials, as they will peskily inch their way in front of you at the worst possible time, deflecting your Truth Bullets.