The whistle that heard is in this sound effect, along with the other variants from the Series 6000 library, is a fouled Canadian National 5 chime step-top steam whistle, which was recorded from Canadian National Railway S-1-b class 2-8-2 "Mikado" type steam locomotive No. 3254 in the 1980s. Eventually, it would get replaced by a better tuned whistle, due to the old one being a bit too loud and squeaky.
The site/location where the sound effect was recorded was probably at the Steamtown USA in Scranton, Pennsylvania.
As of now, this sound effect is the most commonly used train whistle sound effect, as it has made a number of appearances across 100+ pieces of media.
Clean, Full Length and Unedited Link to the Sound Effect[]
Clean, Full Length and Unedited Link to the Sound Effect
Thomas & Friends (Used as Rocky's whistle in a normal pitch in series 10, Ferdinand and Lorenzo's whistles in a low pitch and Marcia and Marcio's whistles in a high pitch.)
ToddWorld (Heard once in "A Trunkful of Trouble".)
LEGO City Mini Movies (Heard in "Train Ride" and "Night Shift", despite being dubbed on a diesel locomotive and an electric high-speed train respectively.)
Runaway (2009) (Shorts)
Technological Threat (1988) (Used for the Dweeb; 2nd and 1st whistles only; used for the Blocky Boss when he fell down a trapdoor.) (?)
Video Games[]
Video Games
3DS:
New Super Mario Bros. 2 (Used every time Iggy and his Chain Chomp get hit during their boss fight.)
Super Mario Galaxy (2nd whistle only, higher pitch; used whenever a Wiggler becomes enraged.)
Super Mario Galaxy 2 (The 2nd whistle is used in a normal pitch whenever Gobblegut blows smoke out of its nostrils and in a high pitch whenever a Wiggler becomes enraged.)
Brooklynn The Cartoon Girl (Heard once in "My Little Pony: Mobile Game's "Missing Wings and Maze-y Things" Finally Worked!".)
CBProductions # (Used when Christopher Biello shouts "Woo woo!" in Visiting The Greenberg Great Train And Toy Show In Wilmington, Massachusetts (Trailer) and can be heard on some Development Streams, Random Roblox Games Streams and whichever stream it is heard in.)
SMG4 Videos (1st whistle only, heard once in a low volume in the background in "Mario's Train Trip", after Mario walks inside the caboose at the end of the train going to "Uniderpal Studios".)
SML Videos (Heard once in "Bowser Junior Pierces His Nose".)