This sound effect can be found on Rocky and Bullwinkle and Friends Sound Effects Library, which was made by Sound Ideas. The sound effect is same as the second half of Sound Ideas, ELEPHANT - FOUR TRUMPETS, ANIMAL on the Hanna-Barbera Sound Effects Library. Links: https://soundeffects.fandom.com/wiki/Sound_Ideas,_ANIMAL,_ELEPHANT_-_ELEPHANT_TRUMPET,_CARTOON#Audio_Samples