Nikon's DSLRs make a clunk: http://www.youtube.com/watch?feature=player_detailpage&v=fz9JHIX7Big#t=51s
while
Cannon's DSLRs make a chirp: http://www.youtube.com/watch?feature=player_detailpage&v=c8c7I5c_pY0#t=12s
while
Cannon's DSLRs make a chirp: http://www.youtube.com/watch?feature=player_detailpage&v=c8c7I5c_pY0#t=12s