Is that spooky old house full of ghosts, or just infrasound?

[MUSIC PLAYING] FLORA LICHTMAN: Hey, it’s Flora, and you’re listening to Science Friday. Old, creepy houses are a horror cliche. But why? Why do old, abandoned houses freak us out? My next guest has a theory, and it has to do with a rumble that you cannot hear, but is very real. Dr. Rodney Schmaltz, Professor of Psychology at MacEwan University in Edmonton, Alberta, is here to tell us about his new research. He studies pseudoscience. Rodney, welcome to the show.

RODNEY SCHMALTZ: Happy to be here.

FLORA LICHTMAN: Do you think of yourself as a ghostbuster?

RODNEY SCHMALTZ: I do not. I am an educator. [LAUGHS] But I teach a class on scientific skepticism, and we do, in fact, go ghost hunting to debunk the tools you see online and on TV. But I would say what I do is a little bit different than ghostbusting.

FLORA LICHTMAN: Do you have an interest in spooky things, spooky houses?

RODNEY SCHMALTZ: I’m interested in why people have these experiences. So I haven’t seen any good evidence for the paranormal or for ghosts, but I do believe that people are genuinely experiencing something, and that’s what I’m interested in. What’s that something? Why do people feel like they’ve had these experiences?

FLORA LICHTMAN: Well, let’s get into your study, because you had a hypothesis that people are feeling something. What were you testing?

RODNEY SCHMALTZ: We were looking at the impact of infrasound. And infrasound is a low-frequency sound below 20 hertz. We can’t consciously hear it, but we can feel it. The way I like to describe it is imagine you’re at a concert and there’s a lot of bass, and you kind of feel that tension in your chest, and the hair on the back of your neck might go up. But you know what it’s from. It’s from the music.

But imagine a lower level experience like that. Maybe not quite as intense, but you can’t hear anything. And infrasound is caused by things like, in old buildings, there’s low rumbling pipes, or it could be old boilers. As well, it’s caused by heavy machinery, traffic. So it’s kind of all around us.

So in our research, what we did is we brought people into the lab, and we exposed them to infrasound or not. And we did that in the presence of relaxing music or more ambient, spooky sounds, the kind of thing you’d hear in the background of a horror movie.

We took a number of measures, including cortisol. And cortisol is a hormone associated with stress. And what we found was that regardless of the type of music you were listening to, be it creepy or relaxing, cortisol levels went up. On top of that, across both conditions– so across both types of music, people rated the music as sadder, and they found it less interesting as well. They reported just generally feeling more irritated in the presence of infrasound.

FLORA LICHTMAN: Hmm. So it’s having an effect on us, whether we’re cognizant that it’s happening or not.

RODNEY SCHMALTZ: Exactly. And I think it could at least partially explain some hauntings in that sense. So as you said, if you walk into an old building and you don’t know what infrasound is, which most people don’t, you’re feeling something. Especially if you’re going to the basement, there’s a really good chance that there’s some low rumbling pipes down there or an old boiler. And if the setting is right– so it’s dark, it’s creepy, you feel something– it’s quite reasonable for someone to believe that they’ve experienced a haunting, when in fact, what they have experienced is an old boiler.

FLORA LICHTMAN: Did you measure infrasound in old houses?

RODNEY SCHMALTZ: That’s actually our follow-up study. So we are looking at that now. We are going to different supposedly haunted locations here in Alberta, and we have control buildings that are not supposedly haunted. And we’re looking to see if the infrasound levels are higher in these supposedly haunted places than places that aren’t. So we just got started on that. We’ve only gone to about four, I think maybe five locations now. So it’s on its way. We’re looking to see if there are any differences there.

FLORA LICHTMAN: Is it difficult to measure infrasound?

RODNEY SCHMALTZ: It is difficult. You need specialized mics for that, and they’re quite expensive. But if you want to see if there’s some infrasound, what you can do, if you just light a candle or have a lighter and the flame starts to bend kind of in the middle, that’s a sign that there’s infrasound. And if it kind of bends and then starts turning almost, it looks like it’s turning, that’s a good sign there’s infrasound as well. So it won’t tell you how much, but at least you know that there’s a good chance that there’s some infrasound present.

FLORA LICHTMAN: That’s also a sign of ghosts.

RODNEY SCHMALTZ: [LAUGHS] The spinning flame does seem ghost-like, but I assure you, it’s not. It is caused by infrasound.

FLORA LICHTMAN: Are we encountering infrasound in other places?

RODNEY SCHMALTZ: We are. There’s infrasound all around us. Traffic generates infrasound. Subways could generate it, heavy machinery. So it’s around. One interesting aspect of our study is to also look at it in the context of noise pollution. So is this infrasound impacting people?

Now, I don’t want to go beyond our data, so I can’t definitively say. But what we found was that at least in a five-minute exposure, cortisol levels went up a little bit. Now, it could be the case that when people are exposed to it for longer periods of time, maybe they habituate. Or it could be the case that maybe over longer periods of time that there’s this kind of cumulative effect, and people just feel some stress.

So we know there’s some research showing that people tend to feel more stress in urban rather than rural environments. But this wouldn’t explain all of that, but maybe it would be a small piece of the puzzle. But definitely more research to be done before we can make any claims either way there.

FLORA LICHTMAN: You know, big picture. Tell me about how this fits in with your research generally, this haunted house study.

RODNEY SCHMALTZ: [LAUGHS] Well, I’m interested in why people believe in things that don’t have good evidence. So helping people become better consumers of information. And once people believe something, we know it’s really hard to change their minds. And part of the reason is that when you tell someone that something is false, say that ghosts don’t exist, you’ve created this cognitive gap. So they’ve experienced something. It felt ghost-like. And then somebody comes along and says, there’s no evidence for ghosts. It’s like, well, then what did I experience?

So I hope research like this will give people at least some pause to think, OK. Maybe what I experienced is an old, low rumbling pipe, or an old boiler. So what we’re doing then is helping fill in that cognitive gap. So my colleagues are more interested kind of in the noise pollution side. I’m more interested in the education side and giving people explanations for supposedly paranormal events.

FLORA LICHTMAN: Yeah, and taking people’s experiences of the world seriously enough to investigate them.

RODNEY SCHMALTZ: Absolutely. Like I said, people are experiencing something. It’s a genuine feeling. And we know from past research that expectation is a huge driver of experiencing anomalous or paranormal things. So if you’ve been told a house is haunted and you go into the basement and you feel something, it’s very reasonable to think that it is ghostly, when again, it could just be a factor of the environment in an old building.

FLORA LICHTMAN: Hmm. Really interesting, Rodney. Thank you for taking us through it.

RODNEY SCHMALTZ: Oh, happy to do it.

FLORA LICHTMAN: Dr. Rodney Schmaltz, Professor of Psychology at MacEwan University. After the break, looking for infrasound in nature from volcanoes, earthquakes, even asteroids. Do not go away.

[MUSIC PLAYING]

Infrasound isn’t just rumbling out of the basements of old spooky buildings. It’s all around us. And my next guest studies infrasound in nature, the low, low-frequency groans from volcanoes and earthquakes and even asteroid impacts. Dr. Milton Garcés is the Director of the Infrasound Laboratory at the University of Hawaii. Milton, welcome to Science Friday.

MILTON GARCES: Thank you.

FLORA LICHTMAN: I’ve heard you describe yourself as a sound hunter. Tell me more.

MILTON GARCES: There is this zoo of infrasound out there, and most of it, we’re familiar with. And then there’s all this exotic creatures out there. Some of them are known, but reemerge out of hiding occasionally, and some of them have not been heard in a very long time. And when they do emerge, you don’t recognize them. And so–

FLORA LICHTMAN: What? Give me an example. What are we talking about?

MILTON GARCES: Oh my goodness. One of my favorite sounds, which is so deep that I have failed repeatedly to try to ensonify it, is the sound from the 2022 eruption in Tonga. We hadn’t heard a sound like that in over a century, since Krakatau.

And when it came up, we have a whole generation of scientists that only knew this signature from the lore of it, written in Royal Society journals, right? [LAUGHS] And to see them from old-timey paper, scratches too, recording it literally in full digital glory, recorded as it goes all around the world, we hadn’t seen that in centuries. So for us, it was a moment of, oh, is this what I really think it is?

FLORA LICHTMAN: Well, where does infrasound show up in nature? Give me some examples.

MILTON GARCES: Oh, it’s everywhere. You first perceive it in the heartbeat of your mother. If you’re sitting there breathing, even walking, a lot of our biorhythms are infrasonic in nature. But we kind of– we’re just used to them, right? Even a deeper level, the sound of the ocean, it contains massive amounts of infrasound, right? The air moving around us.

And what we’ve done as a species is our ear does not respond very well to those sounds, because there’s so much of them. So we are immersed in this inaudible sound field all the time.

FLORA LICHTMAN: We’re immersed in this inaudible sound field. So we can’t hear it, but can we sense it consciously?

MILTON GARCES: We can when it exceeds our threshold of comfort.

[LAUGHTER]

We are– we’re finely tuned species, right? As soon as infrasound gets a little louder, we perceive it through vibration of our body. And usually, when infrasound is loud enough, it leaks into the audio range. So you start hearing it as a bass tone, right? And so that’s when we begin to sense it. As soon as it increases past our threshold of comfort, then it’s like, oh, there’s something happening. And it can be very unnerving, because what generates infrasound is usually bigger and stronger than us, right? We’re talking about the forces of nature. [LAUGHS]

FLORA LICHTMAN: A volcano.

MILTON GARCES: Yes. An elephant. [LAUGHS]

FLORA LICHTMAN: An elephant. Yeah, OK.

MILTON GARCES: [LAUGHS] Big things, often moving fast, right? An asteroid. Doesn’t have to be big. But if it’s moving really fast, it has a lot of power, and it will generate infrasound, right? So all these things that are big, hot, or fast can radiate infrasound. And when you hear those coming, it’s fair warning, right? [LAUGHS]

FLORA LICHTMAN: Well, I wanted to ask. Is that part of the interest in studying it? Can you use infrasound to predict that a volcano’s going to erupt, or can it tell us about these phenomena in a different way?

MILTON GARCES: In some ways it can, yes. In fact, one of the most important applications of infrasound is to provide early warning of an ongoing large eruption so that aircraft can deviate from their paths and avoid the ash that comes with it. That is a very tangible application, and that is basically now in our toolkit for protecting lives and property, right? And so that’s one of them.

Another application that came very much to the fore with the Tonga eruption in 2022 is if you have a big eruption in the middle of the ocean, it will generate a tsunami. And so the sound from the eruption precedes the tsunami by a substantial amount, and that’s also early warning.

FLORA LICHTMAN: Mm. I mean, how far s infrasound travel?

MILTON GARCES: If it’s big enough, it will go around the world multiple times. [LAUGHS]

FLORA LICHTMAN: Wow.

MILTON GARCES: So yeah, there’s that.

FLORA LICHTMAN: Wow. I mean, so do you have– how do you collect these sounds?

MILTON GARCES: So at the turn of the century, we deployed the International monitoring system to monitor clandestine nuclear tests, which has an infrasound network of arrays, and deployed throughout the whole planet. And so we have global coverage of infrasound, a very high quality. These are exquisite sensors that can pick up almost anything.

FLORA LICHTMAN: You talked about ensonifying infrasound, so taking infrasounds and making them audible to us. We have a clip of one of your recordings sped up so we can hear it.

[AUDIO PLAYBACK]

[LOW RUMBLING]

[END PLAYBACK]

I’m frightened.

MILTON GARCES: Funny story.

[LAUGHTER]

When I arrived in Hawaii before the turn of the century, I was already an infrasound specialist. I was doing infrasound before it was cool, right? So–

[LAUGHTER]

–so I was like, oh, there’s a volcano here. This is awesome. Does it produce infrasound? Everybody told me, no. Kilauea does not produce infrasound. It’s like, hmm, that’s unlikely. So we made the first basically published paper of infrasound from Kilauea Volcano.

And what you’re hearing there is Kilauea in one of its many incarnations, because it’s a dynamic system. And this is what it does all the time. At the time of that recording, it was an open vent. It had been in eruption for over 20 years. And that’s what it was radiating all the time. And so–

FLORA LICHTMAN: All the time.

MILTON GARCES: All the time.

FLORA LICHTMAN: Wow.

MILTON GARCES: Now– I don’t know if you’ve seen the activity– it’s the most predictable it’s ever been. Like, every week now, it erupts. And it’s really cool to observe that. So then it opens up, and [INAUDIBLE]. And what you hear is a variant of that. And it’s echoic, because it’s in a giant caldera, right? So everything rings. So you get this cathedral effect if you listen to it correctly, right?

It takes a lot of effort to ensonify something as grandiose as a volcanic eruption into our very limited response. So the best I can do is take into the bass range, you know? Like, the stand up bass range, and try to make something that conveys that feeling of strength that comes from the sound field.

FLORA LICHTMAN: Wait. Why– is there some creative license in there? Why is it difficult to ensonify it? I would think you just, like– I don’t know– type a number in and say, move it on up.

MILTON GARCES: You would think so, but pitch shifting past a few octaves doesn’t map very well. You have a lot of artifacts. So the other way you can do is transpose, which is basically of a sound compression. And you have to do it in a way that doesn’t speed up too much, because then it’s very short. So there’s some thoughts that have to go into that. Nature gives us what it gives us, and sometimes these raw sounds sound very raw. [LAUGHS]

FLORA LICHTMAN: Hmm.

MILTON GARCES: So you have to capture the elements of that sound that make it really special.

FLORA LICHTMAN: I love that there’s an art to this, to making these inaudible sounds, these secret sounds audible. Do you have a favorite, Milton? A favorite infrasound, ensonification?

MILTON GARCES: You know, the one that still keeps getting away is that Tonga event. I haven’t been able to capture it with that. The central frequency of this, it’s like 30 minutes. It takes so long to just get a cycle on that, right? To transpose that to the audible ranges, it’s such a sonic unicorn. I kid you not.

It’s called the lamb wave, and we haven’t seen something like that in so long that we thought it was mythical, you know? [LAUGHS] And there it comes. And it propagates at the speed of sound, and it looks like sound, but it’s not really sound. This is [INAUDIBLE] acoustic gravity wave as an edge. But it is so exotic. It is the sonic unicorn. I love that thing. [LAUGHS]

FLORA LICHTMAN: The sonic unicorn. Milton, thank you for introducing us to this, and thank you for being on the show today. Appreciate it.

MILTON GARCES: You’re welcome.

FLORA LICHTMAN: Dr. Milton Garcés, Director of the University of Hawaii’s Infrasound Laboratory. One last thing before we go. The weather is getting warmer, which means happy hours, porch beers, fun fruity cocktails.

And we want to hear from you. What questions do you have about alcohol and what it does to us? Call with your question and tell us the personal story that led you there. 877-4-SCIFRI is our number. 877-4-SCIFRI. This episode was produced by Dee Peterschmidt. If it rocked your world, leave us a review. Thank you for listening. I’m Flora Lichtman.

Copyright © 2026 Science Friday Initiative. All rights reserved. Science Friday transcripts are produced on a tight deadline by 3Play Media. Fidelity to the original aired/published audio or video file might vary, and text might be updated or amended in the future. For the authoritative record of Science Friday’s programming, please visit the original aired/published recording. For terms of use and more information, visit our policies pages at http://www.sciencefriday.com/about/policies/