When sound designer Ben Burtt was assigned to make various Star Wars sounds, he went straight for the lightsaber. It took a lot of work to dial in that humming, buzzing, swooshing sound...and Burtt was a grad student at USC while doing the work. In this short video, Burtt walks us through how it all happened:

For more on the lightsaber's backstory, check out this fifteen-minute video which includes Burtt telling some of the same stories, with some added commentary from George Lucas and more footage of the early recording sessions.