This sound effect can be found on the Hanna-Barbera Lost Treasures Sound Effects Library, which was made by Sound Ideas. It includes H-B ELEPHANT - BIG ELEPHANT ROAR, ANIMAL 03, Sound Ideas, ELEPHANT - ANGRY ROARS, ANIMAL and Sound Ideas, ELEPHANT - SEVERAL ELEPHANTS TRUMPETING, ANIMAL. An edited version of this can be found on The Edge Edition Volume 1 as Hollywoodedge, Elephants Trumpet An TE016001. Links: https://soundeffects.fandom.com/wiki/Sound_Ideas,_ELEPHANT_-_TRUMPETS_IN_JUNGLE,_ANIMAL_02#Audio_Samples