title: Debug beeping in Cocoa
body: <p>Sometimes when I press the backspace key, my app... beeps.</p>
  
  <p>Since this beep is not caused by my code (I removed all calls to <code>NSBeep</code>), I suspect the cause is that there is an object responding the the backspace key that shouldn't be.</p>
  
  <p>How can I debug the source of the beep?</p>