http://www.ebay.com/itm/Nathan-Airc...577660?hash=item211228b1fc:g:eLIAAOSwZ1BXcXvf
Dave this should hook you up and wake up the neighbors.
Full on set! Amtrak and the coaster run em http://www.ebay.com/itm/Hornblaster...ash=item2c9f56ce45:g:3H4AAOSwnDxUgd7N&vxp=mtr Rated in miles heard.
The "yo-yo" - HornBlasters.com - for loud you are going to need to spend at least $500 tops. If you DIY you can get usually on ebay an actual train horn, search for leslie train horn.
Also, no one beats this guy: