Actor Seth Green—yes, that one—has seen Godzilla Minus Zero and says it’s awesome.

While introducing the New York Comic Con panel for the 39th film in the Godzilla franchise, Green stressed that the filmmakers behind the movie “have created kaiju that feel physically real and, trust me, emotionally terrifying.”

While a lot of that terror came from the work of Oscar-winning visual effects artist Tatsuji Nojima, some it came from the shrieking of Godzilla and his three-headed nemesis, King Ghidorah. Those roars were the work of sound designer Natsuko Inoue and her team, who created the monsters’ outsize vocalizations by rolling speakers to the top of an outdoor dam—much to the horror of people nearby.

“There were people having a picnic, maybe people just taking a stroll,” Hisafumi Takeuchi, who also worked on sound for the film, said during the panel. “The person walking their dog, though—they had the worst time, because the dog was freaking out and barking back at us.”

Since the creatures are imaginary, getting their screams to sound realistic is essential to making them seem believable—and genuinely scary—onscreen. At first, Inoue wasn’t sure if the idea of recording at the dam would work. Those fears were quickly put to rest.

“The first time we sent that roar out on the speakers, I could see the relief and confidence in everyone’s eyes,” Inoue said. “By using speakers and projecting it into the real world, capturing the reverb, the echo, the reflection of the sound back with the mic, it manifests it in our world.”

For other kaiju sound effects, Inoue’s team took an analog foley approach. To simulate Ghidorah’s dragon-like wings, for example, they flapped a rubber fisherman’s suit and mixed that noise with the sounds of an accordion-like air duct.

Getting two of Toho’s most famous monsters right was a huge undertaking, especially after the success of Zero’s predecessor, Godzilla Minus One, which brought home $114 million worldwide at the box office. Following that 2023 film’s harrowing mix of post–World War II malaise and bracing kaiju destruction will be tough, but a new trailer shown during the film’s panel at NYCC promised a sequel full of aerial dogfights and a punch-’em-up for the ages between Godzilla and Ghidorah.