Without dispute, true crime is stepping out of the shadows. Between last year’s breakout whodunit podcast Serial, the Netflix head-scratcher Making a Murderer, and the FX series The People v. OJ Simpson, millions of listeners and viewers just have to get to the bottom of it.

I’m a natural of the genre, glued to the stuff I mentioned, brushing up on my Errol Morris, and guzzling the streams of Forensic Files, The New Investigators, and Homicide Hunter. The shroud of murder and mystery might hang heavy, but the future of the hard-boiled style looks bright.

There’s one thing I can’t help but notice again and again: the overuse of a distinct sound effect. It’s a squelched young woman’s voice, distorted by static, saying a few numbers in a particular rhythm. There’s no consensus, but to the majority of listeners it sounds like she’s saying, “liberty 285, code 6, 105 North Avenue.”

I’m a gumshoe who generally startles at the sound of police radios—so not only have I noticed this sound effect in true crime reenactments, but also through the background audio of shows, music, videogames, and movies.

Her voice is so distinct. The countless iterations of CSI, basically every episode of Law and Order, many episodes of The X-Files, the dystopian Bruce Willis/Brad Pitt banger Twelve Monkeys, the Nic Cage car chase classic Gone in 60 Seconds, the animated series Batman, the Grand Theft Auto video games series... seemingly anything produced in the ’90s and beyond with some kind of police presence, this woman’s on that tape.

You can see why I’m obsessed. A devil in a police-blue dress.

There’s a small history of sound effects with cult followings. The best example is probably the Wilhelm Scream, a brief, terrified bellow that stems from productions of the 1950s. It is now so ubiquitous that it’s an inside joke in the TV and film industries. (The joke in the case of our missing dame hadn’t yet landed in Hollywood.)

Starting with some well-phrased googling, I learned this gal had driven a long list of people before me crazy. One YouTube clip from 2008 is populated with more than 400 users’ notes on where they’d heard the voice of the airwave angel. The original uploader traced his memory of the sound to an iteration of the video game SimCity. Having also played this obsessively in my youth, I realized the sound was stamped into my prepubescent brain. Love comes early.

Given this, and the sound’s overwhelming use in the proto-reality show COPS, it emerged that it was produced in the early 1990s. It was buried as a file on a sound effect library called The Hollywood Edge, from Disk 15 of The Premiere Edition released in 1991. “Police Radio: Calls Received Through Radio From Female Dispatcher With Static And Squelch Pops; Close Perspective.” That’s the name of the clip.

I had to find this woman.

It was easy enough to track down the current owners of The Hollywood Edge collection. As one of the top sound effects libraries in Hollywood, it has changed hands several times since its formative days in the ’80s. We’re talking tens of thousands of sounds—big money for the movie-making market. That is, if you can keep afloat a company slinging only audio.

It turned out a Canadian company called Sound Ideas acquired the rights to these sounds last year after its previous operators, Todd-Soundelux, entered bankruptcy. I spoke to Peter Alexander at Sound Ideas, a sales manager for the company who was enthusiastic but ultimately couldn’t help. (He was a Canadian, so he was super nice.)

Later, I was told by an anonymous source, “Peter doesn’t have the experience or connections to find that information for you.” Burn. (But also, it was true.) At a different point in the conversation, that anonymous source got spooked, afraid he’d let his mouth run a little too much—he suddenly had to get off the line. I almost felt bad for these guys—they barely knew what they were wrapped up in. Most of the time, truth is stranger than fiction.

Weeks later, I was still looking for her. I’d try to ease my restless mind, and there she’d be: Modern Family, Bates Motel, Max Payne, Superman, The Closer.

There is a soft cabal, if you will, of sound effects designers in Hollywood. Everyone knows everyone, leading from one owner of the sound library, to a manager of the library, to an actual librarian at the Hollywood Edge library. These audiophiles were responsible for cataloging, collecting, curating, and creating sounds during their tenures. So, from stone to stone, I made my way to John Moran, a sound effects professional who was The Hollywood Edge’s managing director from 1994 to 2013.

“That was so long ago, and those records were not retained,” Moran told me. “But there were always people around who were willing to jump in front of a mic. If the sound was created, as opposed to collected in the natural world, a non-union employee probably would have done the voice. So there’s no real way to document non-SAG performers.”

If I could gain just a little more detail on the sound, it was very likely I could find someone who was there—someone who knows to whom this disembodied radio voice belongs. After all, the Hollywood SFX circle seemed to be shrinking, as digital libraries fall away to piracy and bankruptcy.

One of the most in-demand sound designers is Lon Bender. He’s the guy behind the guy behind the guy. He co-founded the Soundelux Entertainment Group in 1982 with Wylie Stateman. That company created the Hollywood Edge.

“Sometimes a sound can take on a life of its own,” Bender said, once I got him on the phone after a real horse race, “much like the sound you’re describing, which I didn’t know until now.”

Bender was just nominated for an Academy Award in sound mixing for his work on The Revenant. It’s his fourth nomination. In 2011, he nabbed one for his work on Drive. In 2007, it was Blood Diamond. And in 1996, he won the Oscar for his work on Braveheart.

“I’m flattered and happy that someone has been listening that closely,” Bender said of the effect, which was released under his watch at The Hollywood Edge.

“Not all people have the budget or time or know-how to record sounds themselves in every instance,” Bender said. “So they go back to their sound libraries. And if we didn’t have specific sounds, in the case of The Revenant, we went out and recorded them.”

He said he and his team recorded the sound of snow falling off a branch. He explained how they pointed their microphones at different actors of different weights trudging through different kinds and different depths of snow, at different perspectives, to capture the cadences.

“Cadence has a lot to do with subtext. The classic example is the cricket. Say there is an outdoor scene with dialogue. And to add a sense of calm, you have a cricket with a calm, an almost pulsing, cadence. But as the scene becomes more tense, the crickets become higher pitched and the cadence speeds up,” Bender said.

We agreed that the rhythm and cadence of the woman on the radio helped to make it so sticky. But Bender’s memory for sounds didn’t extend to the enigmatic dame. “I don’t know anything about the origin of that particular sound. I’m not sure if we created it or if it was recorded in the natural world.”

How could I expect him to remember, really? By the time “Police Radio: Calls Received Through Radio From Female Dispatcher With Static And Squelch Pops; Close Perspective” hit the market, Bender had already been in high demand for more than a decade. Thirty years and probably hundreds of thousands of sounds have passed him by since then.

Luckily, Bender gave me one more lead in the form of Rob Nokes. This guy is a historian of sound effects like you wouldn’t believe, a library so impressive that he says he has 100,000 pages of documentation on sounds, as well as libraries like The Hollywood Edge. (Nokes was the man who saved the Hollywood Edge from bankruptcy in 2014, but doesn’t own it now.)

When I called him up, I told him the name of my mystery sound. Within five seconds, I heard it playing in the background. “It’s true that there’s a cadence to it, but it’s because it’s a short sound,” Nokes said.

He explained that in audio production for TV and film, dialogue, music, and background sounds all come together into one track.

“In my mind, it’s poignant, short and to the point. It’s got a pitch that cuts through the background that makes it noticeable in the audio track,” Nokes said. “You need tracks that are pitched with a higher frequency and less low frequency. It’s a higher-pitched voice, it’s higher frequencies, and it’s short.”

But Nokes took the analysis a step further, ascribing melody to the chatter.

“Songs are pleasant or unpleasant or just standard. This sound, there’s a pattern of pitch that’s pleasurable. And, in my opinion, good sounds evolve over time. And that evolution is pitch, frequency, and volume. So interesting sounds have those dynamics over time. Any change in a sound over time makes it more interesting.”

Essentially, because of the sound’s brevity, rhythm, and rapidity of change, the radio chatter will be with me until I die. At this point, I still had no face to match her voice.

“In the ’80s and ’90s,” Nokes told me, “there was less awareness of copyrights and mechanical copyrights. So it’s possible that someone took a scanner, recorded some random police voice, and published it. That sounds authentic to me.”

And that was that. The sound was probably a field recording.

But there’s no way to know for sure. That’s just the way these things work sometimes. Brendan Dassey? O.J. Simpson? Robert Durst? The Woman on the Radio? Who the hell knows?

A couple hours before I wrapped, Nokes emailed me. The trail finally went cold. He told me he contacted Mark Ormandy, the original Soundelux librarian. There was no further information we could gather. Since I didn’t know where or when the sound was recorded, I had to stop short of contacting nearby police precincts to find out who was working the radios that day.

But there’s no statute of limitations on a missing persons case. This one’s still open. I am still missing this person. I’ll sleep when I’m dead.