Show #1583 is primarily famous for the birthing of the Marsupial Gurgle sound that is site is named after. Before that sound was made, Andrew did make a sound that could very well be considered an ancestor to the Marsupial Gurgle:
At the 47m 24.519s mark of show #1583, Andrew Walsh made an interesting sound that wasn’t commented on until show #1584. The sound ended up being named both “Marsupial Gurgle” and “Barabajagal“.
As mentioned, the Marsupial Gurgle sound was not commented on until a listener sent in an e-mail asking what that sound was and described it as a “sweet gurgle of an infant marsupial”