What is the ruling on a man imitating a woman's voice, and what is the ruling on listening to an audio clip of a man imitating a woman's voice for a prank?

It is not permissible for a man to imitate a woman's voice, because it constitutes imitating women, which is forbidden. Listening to such clips is impermissible due to the Sharia violations they contain, such as mockery. The prohibition becomes even more severe if the intention behind it is to arouse desire. Imitation is forbidden even if it is unintentional.