When you put JTextField to your frame as you did in your code, it's placed at the top of the frame (north) and centered horizontally. Since you created text field of width 400 (characters) it's to wide so you're seeing just the middle part of it, and the beginning (where the text should appear) is hidden.
Put smaller value in the constructor of text field and you should be able to see it. If you want it to be as wide as the frame then change the layout of its parent panel (e.g. to GridBagLayout).
The quieter you are, the more you are able to hear.