Purring, basically! They rub their pedipalps to make the initial vibration that is then amplified by dead leaves and such.
http://www.smithsonianmag.com/smart-news/listen-dulcet-purr-wolf-spider-180955482/?no-ist
I recall my first time pretending to be a Giant Spider years ago. I basically spoke using heavy Vs and Zs, mimicking a vibration-based speech. Yay me!
Well dankity bling-bling!
For me, Great Spiders always conjure the Giant Intelligent Friendly Talking Spiders of the Exile games from Spiderweb Software. High-pitched, excitable, brimming with wide-eyed joy and slight idiocy. “Hi! You’re cute!”
I imagined them making lots of rapid clicking sounds with their mouthparts.
Wayfarer, those were some of my fav games back in the day!
Spiderweb’s games are still my among favorites, and I’m actually really sad that those spiders haven’t shown up in any entirely new games for years and years.
Spiders don’t have mouth parts. They have a hole bristling with the little hairs through which they suck your dissolving innards.
They have palps and coxae! Which, okay, aren’t technically part of their mouths, but they’re around the mouth and can make clicking noises.
At least some types of chelicerae look eminently clickable, too.