Don't know, my dog never howls but he guard barks good.
Also, I deliberatey conditioned him to bark at the Coronation St. end tune as i let him out for toilet at 8pm. when corrie is delayed so is he can tell the difference between start Corrie tune [no bark] and end Corrie tune [mucho bark] even if the time slot is wrong. I can't tell the diff between those 2 tunes, thought they were the same. he doesn't bark for the ads break Corrie theme either? Also some dogs watch tv, mine can't took him a year to learn how to see through a window.. :-)