It’s a good headline. Pity the purr isn’t really like a cat’s purr! The male wolf spider (species: Gladicosa gulosa) creates this sound, which we can unusually hear, by vibrating the surface he is on, so the surface has to be suitable.
The spider picks up the vibrations through body sensors and does not hear the sound in the conventional way. The female who is being courted can only ‘hear’ the sound if she is on the same surface as the male making the sound.
This picture is here in case the video disappears. Sometimes they do.