The Instrument Rating Application (Form 645) item 34 for the NDB requires the ident to be monitored during approach. Item 57 requires the correct identification of navigation aids used.
Thats all fine and beaut, however as I said and a post or two below me have said, you do not have to monitor the
aural ident in
some modern aircaft as the avionics identify the aid for you. They will also indicate a fail, the needle simply dissapears from the screen.
So it is identified by confirming the identifier, i.e. using the Howard Springs NDB you would expect to see
HWS on your Nav display, if it fails then HWS will dissapear AND the needle will no longer be visible. That meets the requirements above without monitoring or even listening to the aural ident.
Now I am speaking from a jet perspective, and i'm not current on light aircraft, but I believe that some of them have some reasonably good gear so maybe they do the same.