Siren, whistle (6)
I believe the answer is:
hooter
I believe this is a double definition.
'siren' is the first definition.
(hooter can mean a siren or alarm)
'whistle' is the second definition.
(thesaurus)
(Other definitions for hooter that I've seen before include "One scents" , "Siren; nose (sl.)" , "it smells" , "Uphill stone pusher (Gk. myth)" , "It makes a loud noise" .)