For hundreds of years, residents of a small New England town have been hearing strange noises coming from the earth.

Reporter Ari Daniel took a trip there, to Moodus, Connecticut, to check out the reports. He produced the story for Stylus, WBUR’s experimental documentary series about sound, music, and listening.

The piece features the voices of Cathy Wilson, Moodus resident; Alison Guinness, historian; and John Ebel, seismologist, Weston Observatory, Boston College.

Reporter

Ari Daniel, science journalist. He tweets @mesoplodon.

Copyright 2018 NPR. To see more, visit http://www.npr.org/.

ROBIN YOUNG, HOST:

It's HERE AND NOW.

And now an audio mystery. For hundreds of years, residents of a small New England town have been hearing strange noises from the very earth underneath them. Reporter Ari Daniel took a trip to Moodus in South Central Connecticut to find out what is it.

ARI DANIEL, BYLINE: Can you just describe what it looks like out here?

CATHY WILSON: Well, right now...

(LAUGHTER)

WILSON: ...I'm noticing the sky is super blue. It's beautiful. I hadn't been out yet this morning.

DANIEL: Cathy Wilson and I are outside her home in Moodus. She's lived here for 45 years.

Wilson brings me upstairs to the large rec room where, in the early '80s she had her first, I guess you'd call it, encounter.

WILSON: If I remember correctly, I was down in this end, and you can see this end has the most windows. And the four children were finally old enough that they were all in school. I finally had free time, and I finally had quiet.

(LAUGHTER)

DANIEL: So there she is in her rec room with all the windows open. And then Wilson hears something, something odd.

WILSON: Sounds like thunder except it's a bright, sunny, summer day. And there's definitely no sign of thunderclouds.

DANIEL: How close did they seem?

WILSON: They seemed like they were in the backyard.

DANIEL: It sounded like thunder in your backyard.

WILSON: It was just - it was confusing.

DANIEL: But Wilson's not one to stay confused.

WILSON: I'm just a curious person. And if there's something I don't understand, I will try to learn more about it.

DANIEL: So Wilson started keeping track of the sounds, writing down when they happened and what they sounded like.

WILSON: Sometimes it would be just boom. Then there were other times when it was more of a crack sound. And then you'd hear something that really did sound like thunder. It would be a rumble, rumble, rumble, rumble, rumble, boom, rumble, rumble. It would just go on and on.

DANIEL: Wilson was telling everyone in the neighborhood about the noises. Some had heard them. Some hadn't. And she met people on her quest to figure out what they were, like local historian Alison Guinness, who says Wilson wasn't the first person to hear these sounds.

ALISON GUINNESS: The Native Americans who lived here heard those sounds back in prehistoric times. And they would come here and have ritual ceremonies.

DANIEL: I met Guinness outside, near the sacred cave that the Wangunk tribe thought was the source of those strange noises. We don't have their original story. Rather, Guinness says, what we know today is that story mixed with elements from Western legend.

GUINNESS: Their evil god, Hobomoko, lived in the cave with witches. And when he was unhappy with the witches, he would throw the witches out. That would create the noise and the sound that they heard.

DANIEL: The name Moodus is actually a shortened version of a Wangunk phrase meaning place of noises. Later on, the settlers who displaced the Native Americans came up with their own theories about the sounds.

GUINNESS: In the early days, all things were connected to God. That's when the clergymen would use those occurrences to bring their flock into alignment, hoping that they'd be scared to death and come back and behave themselves.

DANIEL: So it was like God was getting angry?

GUINNESS: Yes. As science progressed, those ideas change considerably over time, like the explosion of gases underground, tides and winds.

DANIEL: Even things called carbuncles, smoldering subterranean coals thought to grow in size. Each theory was systematically debunked. But in the end it was science that solved the puzzle.

JOHN EBEL: So you want to hear the Moodus noises?

DANIEL: Yeah, that'd be great.

John Ebel leads me down a hall at the Weston Observatory at Boston College into a room with a really good sound system. His colleague fires up the recording.

(SOUNDBITE OF BIRDS CHIRPING AND RUMBLE)

DANIEL: You hear birds chirping in the midst of a deep rumble, which at first is nothing more than the sound of the tape recorder used to make the recording over 30 years ago. And then you hear it.

(SOUNDBITE OF BOOMING)

DANIEL: What sounds like a quick peal of thunder. But it's not thunder, says John Ebel, who, by the way, is a seismologist. It's the sound of an earthquake.

EBEL: Sound waves in the air and seismic waves in the ground are all the same kind of phenomenon. A seismic wave is a wave that actually compresses and stretches the rock a little bit as the wave moves through. When a seismic wave from an earthquake gets up to the surface of the earth, it shakes the earth. It moves it up and down.

DANIEL: Like the surface of a drum.

EBEL: Like the surface of a drum. So the ground literally acts the way a speaker does and sends the seismic waves from the ground into the air, and that is what we hear.

DANIEL: Most seismic waves are too bassy for us to hear them. But not at Moodus. There the quakes make waves within the range of human hearing. The reason, at least in part...

EBEL: The earthquakes are extremely close to the surface of the earth as earthquakes go. The Moodus noises originate from earthquakes with centers that are down about three quarters of a mile in the earth. And that's shallow.

DANIEL: The Weston Observatory got involved in the Moodus earthquakes in the early '70s. A nuclear power plant was operating a few miles away from Moodus and the Nuclear Regulatory Commission wanted to locate the fault that was generating the quakes.

EBEL: Because if we can find the fault, then we can assess its size, its past history and what its potential for future earthquakes might be.

DANIEL: Then in the '80s during a swarm of small earthquakes, Ebel got a call from a handful of Moodus residents, including Cathy Wilson. By that point she'd figured out that the noises she was hearing had something to do with seismic activity. So she gave Ebel a ring.

WILSON: And I told him all the different ones that I had heard, and he said every single one was an earthquake. But how are you hearing them? He said nobody else in town is hearing them. So I explained where I lived, and he said, aha.

EBEL: I knew she was very, very close to the epicenter of these.

WILSON: The earthquake epicenter is about 1,500 yards from my house.

DANIEL: So now, did you get to be known around town as somebody associated with this or...

WILSON: Yeah. I'm the earthquake lady.

(LAUGHTER)

DANIEL: Ebel asked the earthquake lady to make some recordings, but she only ever got a single Moodus noise on tape, that one I played earlier. Now, this isn't the only place where people have heard earthquakes or where earthquakes happen at such a shallow depth. But the fact that Wilson was able to hear such faint earthquakes...

EBEL: Down below magnitude zero.

WILSON: It's almost like a little burp.

DANIEL: ...was a huge help to Ebel.

EBEL: Moodus is the first place where we were able to get firsthand observations by human beings of the earthquake sounds and match them up perfectly with a seismographic data.

DANIEL: But since the early '90s, Moodus has gone quiet.

WILSON: I haven't heard a peep since then.

DANIEL: And yet, says historian Alison Guinness, the legacy of those sounds endures here.

GUINNESS: That's what the teams call themselves, the little noises. So the high school basketball team is called The Noises. And the local drum and fife corps is very well known, and they call themselves Thunder in the Valley.

DANIEL: Because these noises have become so much a part of the lore here, Guinness says she misses the mystery.

GUINNESS: The scientists figured it all out. It's kind of like coming to the end of a journey. And then what do you do?

DANIEL: Yeah.

GUINNESS: It's the getting there, not the being there.

DANIEL: Because once you're there, it's time to look for the next mystery.

GUINNESS: Yes. Exactly.

DANIEL: John Ebel, the seismologist, disagrees. He says there's still plenty of mystery right here in Moodus, because even though we know the sounds are caused by shallow earthquakes, Ebel and his colleagues still haven't been able to pinpoint the fault that's responsible, which means maybe a brand-new fault is forming in the rock.

EBEL: For me the mysteries are different. Why are these earthquakes happening here? Why aren't these earthquakes happening on the local faults? It's shaken loose more questions that I would like to have answered.

DANIEL: And if history gives us any indication, the question surrounding Moodus will continue to rumble far into the future.

YOUNG: Fascinating. Reporter Ari Daniel. His story about the mysterious sounds in Moodus, Connecticut is part of an audio project called Stylist. It's a new series about sound and music. You can go to hereandnow.org to find a link to the Stylist tumbler. HERE AND NOW is a production of NPR and WBUR Boston in association with the BBC World Service. I'm Robin Young.

JEREMY HOBSON, HOST:

I'm Jeremy Hobson. This is HERE AND NOW. Transcript provided by NPR, Copyright NPR.