On October 30, 1939, radio history was born when Orson Welles pranked the nation with a hyperrealistic broadcast of The War of the Worlds. The stunt didn’t cause people to hunker down in fear of an alien invasion, as the apocryphal story goes, but it did cause the FCC to get radio stations to agree not to use fake news bulletins in the future. Clearly, Welles and federal regulators knew that radio was a powerful medium—but the show wasn’t the only one of its era to use sounds to manipulate the psychological state of its audience. As Neil Verma writes, the era’s radio dramas became a way for broadcasters to get into the minds of listeners…and to comment on the very influence of radio itself.

Verma looks at the ways in which broadcasters like Welles and his ilk used sound effects to signal spatial relationships and convey stream-of-consciousness trips through realistic, but imagined spaces. Lucille Fletcher, who was married to Welles protegé and later Hitchcock composer Bernard Herrmann, took the concept one step further with a play called “The Hitch-Hiker,” which was featured on Orson Welles’s show and later adapted for the Twilight Zone.

The play portrays a driver who keeps seeing a mysterious hitchhiker as he drives further and further into eventual madness. It puts listeners into the driver’s mind with close, almost internal sound effects, writes Verma, and plants unease and drama with conflicting sound effects that make the journey more and more surreal. “Fletcher’s play offers no external space, so the chime cannot emanate from outside of [the driver’s] mind,” writes Verma—a break from previous radio drama styles.

These “signals,” says Verma, not only created a claustrophobic and intense psychological effect, but influenced other radio dramas of the wartime era. He ties them to the growing impact of radio itself, noting that “by showing individual signals dominating a mind, radio plays made it seem that mass appeals could also dominate many minds.” Listeners experienced a kind of meta awareness of radio’s influence even as they themselves were influenced on a personal level by the creepy disorientation of Fletcher’s play and others like it, turning radio into much more than an individual experience.

Radio had other powerful impacts during World War II, from “Axis Sally”’s unsettling Nazi propaganda to FDR’s morale-boosting fireside chats to Truman’s sobering announcement of the atomic bombing of Hiroshima. But the pioneering use of sound by dramatists like Fletcher showed that mass media broadcasts could be personal, not just political. Try listening for yourself and you’ll understand just how impactful—and creepy—a half hour with the radio could be.