This 13 June 2019 video says about itself:
Frida Kahlo‘s only known voice recording possibly found in Mexico
The National Sound Library of Mexico has unearthed what they believe could be the first known voice recording of Frida Kahlo, taken from a pilot episode of 1955 radio show El Bachiller, which aired after her death in 1954. The episode featured a profile of Kahlo‘s artist husband Diego Rivera. In it, she reads from her essay Portrait of Diego.