Everybody knows the humming, sparking swoosh of the lightsabers from the Star Wars series. But do you know how that sound was created?

The recipe, sound editor Ben Burtt has said, was the humming of old movie projectors (Burtt was a graduate student working as a projectionist at the time) mixed with the buzz from a microphone as it picked up interference from a nearby TV.

That’s an example of the unexpected, serendipitous way that many classic movie sounds come together—a combination of commonplace and exotic sources manipulated through creative ingenuity. We talked to three of Hollywood’s top sound designers—Erik Aadahl (Argo, the Transformers trilogy), Michael Babcock (In Time, War of the Worlds), and Richard King (The Dark Knight Rises, Master and Commander, Signs)—to find out about the surprising origins of some other cinema sound effects.

(Visit Dolby’s blog to learn more about the role of sound editors and mixers and how a movie gets its sound.)

It’s raining frogs in Magnolia

While sometimes it really does rain frogs, when writer-director Paul Thomas Anderson wrote the phenomenon into the end of Magnolia, Richard King didn’t have time to wait for an amphibian downpour.

Instead, three-time Oscar® winner King spent the day bouncing objects off hams and frozen chickens to get the sound of “really big, organic impacts.” He fed those sounds into a keyboard’s sampler and tried distorting them but didn’t get quite the results he was looking for. Finally, King’s team played the sounds from a speaker and recorded it as they drove by in a car to get a sense of movement.

“In that way, we made the sound sort of real—it’s hard to buy the whole concept to begin with, so I was really leery of doing anything fake sounding, so it had to really sound like frog rain.”

Alien tripods in War of the Worlds

Michael Babcock was responsible for creating a host of terrifying sounds for Steven Spielberg’s War of the Worlds.

But the sound that he’s most proud of, says Babcock, “is the sound the tripods made every time they moved.” As the giant machines stalked humans, the sound you hear is a combination of trains, roller coasters, and a bicycle chain—all of which were fed into a sampler and performed at various speeds with a keyboard controller, creating what Babcock fondly calls “a futuristic, oppressive waltz.”

Meanwhile, Richard King created the deep, bellowing horn sound the tripods used to communicate. To create it, Babcock, a three-time Emmy® nominee, combined sounds of the didgeridoo, an Australian wind instrument, with those of a djembe drum, a rope-tuned skin-covered goblet drum from West Africa played with bare hands.

Bane’s bellow in The Dark Knight Rises

In The Dark Knight Rises, Richard King found that people had trouble understanding what masked villain Bane was saying. “It was just a function of the psychological effect of not being able to see his lips move,” King says. The veteran sound editor tried a number of techniques that didn’t help. Then his team hit on a simple, but surprisingly effective solution—they played Bane’s voice out of three speakers in the front of the theatre rather than the typical single speaker.

“We had to overcompensate with those front three speakers, and that not only made him clearer—it gave him size and differentiated him in sound and tone from Batman and the other characters, and ended up making him more menacing.”

The voices of the Transformers

Erik Aadahl gave each of the robots in the three Transformers films its own sound. “The whole philosophy was that the sound should illuminate the soul of each character,” says Aadahl, who has been nominated for Oscars for Argo and Transformers: Dark of the Moon.

Take Bumblebee, for example, a fan favorite and the most emotional of the robots. To create his signature sound as Bumblebee transforms himself from robot to Camaro, Aadahl wove in the buzzing of bees.

Bumblebee also has an irrefutably adorable whimper when he’s sad. For this sound, Aadahl called on a familiar source. “I used my dog, Freya, and ran his whimper through robotic processing. I like sounds that engage emotionally, and for me, that sound had a very emotional component. In fact, I try to put my dog into every movie I do.”

The leader of the Autobots, Optimus Prime, has a sonic signature as well—air. “He’s based on a semi[trailer] truck, so we use a lot of pneumatic sounds,” Aadahl says. Aadahl managed to get “deep metallic resonances” for the heroic Autobot by recording the hissing and clunking of an old hot water heater in its death throes at his parents’ house.

Perhaps no Transformer has a more interesting sonic backstory than the leader of the evil Decepticons, Megatron. His sonic signature is appropriately violent—the sound of blades slicing and scraping—but it’s his breathing that inspires terror. To produce that sound, Aadahl used an asthmatic tiger.

“He had this ominous inhale and exhale, which was very animalistic,” Aadahl said of the wheezing cat. “We treated it in a way that it would sound like it was coming out of this big metallic hull of the character.”

Alien ambles in Signs

The audience doesn’t see the aliens in M. Night Shyamalan’s Signs until the very end of the film. But they hear them walking outside the characters’ house. So Richard King was tasked with coming up with walking noises for the aliens so weird and creepy that the sound alone would scare moviegoers.

King got goat and horse legs from a taxidermist and recorded his team “walking” the legs around on the set. “We wanted it to sound solid, not fleshy, but organic.”

The sound of the future in In Time

Creating sounds for futuristic movies isn’t always about generating odd beeps, blips, and spacey hums. As Michael Babcock learned from In Time’s writer-director Andrew Niccol, just displacing a sound can create the odd sensation of something that feels almost right but doesn’t quite belong.

For In Time, Babcock took the sound of sirens from China and the Czech Republic and matched them with police cars set in North America. He also took ringtones from European phones and matched them with the American phones in the film. This simple method created sounds that felt recognizable but slightly off, just the way the near future might feel.

The singing of the rigging in Master and Commander

For Master and Commander: The Far Side of the World, Richard King needed the sound of wind whipping through a ship’s rigging. So he and his team built a big wooden box, which they threaded with a thousand feet of rope cinched as tightly as possible to simulate a ship’s rigging. They put this contraption in the open cab of a pickup truck and drove it 50 miles per hour into a 20-mile-per-hour wind, getting seventy miles per hour worth of wind speed.

“It was so loud, you didn’t even hear the truck; you just heard this singing and sighing sound,” King says.