Infrasound is sound below the range of human hearing, generally defined as frequencies under 20 Hz. You cannot “make” infrasound with ordinary speakers, pipes, or fans in any reliable way. Subwoofers, pipes, and fans can all move air at low frequencies, but producing true, usable infrasound requires large air displacement, long wavelengths, and equipment most people do not have. This article explains the physics honestly, separates real engineering from viral claims, and covers what these devices can and cannot do.
What Is Infrasound and Why Is It Hard to Produce?
Infrasound is acoustic energy at frequencies below 20 Hz. The commonly cited 20 Hz boundary is not a sharp wall. It marks roughly where average human hearing fades out, and sensitivity to low frequencies varies a lot from person to person.
The core problem is physical. Sound is a pressure wave moving through air. Lower frequency means longer wavelength. At 20 Hz, one wavelength is about 17 meters, or roughly 56 feet. At 10 Hz, it doubles to around 34 meters. To radiate that energy efficiently, a source generally needs to be a meaningful fraction of the wavelength in size, or move a very large volume of air.
This is why a normal subwoofer cannot do it. A subwoofer reproducing 40 Hz is already working hard. Pushing the same driver down to 15 Hz usually means the output collapses, the cone moves farther than the motor can control, and you get distortion rather than usable low-frequency energy.
There is also a perception issue. Even when infrasound is present, people often do not hear it. They may feel pressure, unease, or nothing at all. That makes “did it work?” a genuinely difficult question without measurement equipment.
Can a Subwoofer Actually Produce Infrasound?
Yes, in a limited and usually impractical way. A subwoofer can produce some output below 20 Hz, but the amount is typically small and the cost is high.
Three things determine whether a subwoofer reaches infrasonic range:
- Cone area and excursion. You need to move a large volume of air. That means a big driver, a long throw, or several drivers working together.
- Enclosure design. Sealed boxes roll off gradually. Ported and horn-loaded designs can extend lower, but they are large and finicky.
- Amplifier power and headroom. Low frequencies demand far more power for the same perceived loudness.
Some hobbyists build “subwoofer towers” using multiple large drivers to get measurable output in the teens. This is real, but it is a serious project. It requires measurement tools, careful room placement, and a tolerance for very large boxes.
One clarification worth stating plainly: many products marketed as “infrasound generators” produce strong vibration and pressure, not true infrasound. Vibration you can feel through a floor is not the same as acoustic energy below 20 Hz. The two get conflated constantly.
Can Pipes and Tubes Generate Infrasound?
Pipes can resonate at very low frequencies, and this is a well-documented physical effect. The catch is that resonance is not the same as efficient radiation.
A tube open at one or both ends has a fundamental resonance tied to its length. A very long tube — several meters — can resonate at frequencies in the infrasonic range. This is why large organ pipes, long tunnels, and big industrial ducts can produce or transmit very low-frequency sound.
For a home project, the practical limits are obvious. A pipe long enough to resonate at 15 Hz is roughly the length of a small room. Even then, a resonating pipe radiates sound poorly at those frequencies because the opening is small compared to the wavelength.
What pipes are genuinely good at is transmitting low-frequency sound rather than creating it. Long ductwork and tunnels can carry infrasound from a source to a listener far away. That is a transmission path, not a generator.
Do Fans and HVAC Systems Create Infrasound?
Yes. Rotating machinery commonly produces low-frequency sound, and large fans, compressors, and ventilation systems are among the more common real-world sources.
The mechanism is straightforward. A fan blade passing a fixed point creates a repeating pressure pulse. The frequency depends on how fast the fan spins and how many blades it has. Slow-turning, large-diameter fans can produce pulses in the low-frequency and sometimes infrasonic range. Wind turbines are a frequently studied example, though the research on health effects remains mixed and contested.
This matters for a practical reason. If you are trying to detect or reduce infrasound in a building, fans and HVAC equipment are often the actual source. That is a real, measurable phenomenon. It is also why “make infrasound with a fan” is partly true — but you are not building a generator. You are observing something the equipment already does.
What Equipment Would You Actually Need?
Producing measurable infrasound at home is possible but demanding. Here is what the task realistically involves.
| Requirement | Why It Matters |
|---|---|
| Large air displacement | Low frequencies need volume, not just power |
| Very large enclosure or horn | Efficient radiation needs size relative to wavelength |
| Substantial amplifier power | Low-frequency output is power-hungry |
| Measurement microphone | You cannot hear infrasound reliably, so you must measure it |
| Analysis software | Confirms what frequency you actually produced |
The measurement point is the one most people skip. Consumer microphones often roll off below 20 Hz, so they cannot confirm infrasound even if it is present. You need a microphone rated for that range and software that can display a spectrum.
Without measurement, you are guessing. Many people believe they have built an infrasound device when they have actually built a loud, vibrating box that produces audible and tactile energy in the 20 to 40 Hz range.
Is Infrasound Dangerous?
This is where claims get ahead of the evidence. Infrasound at high enough levels can cause discomfort, and some people report symptoms like unease, pressure in the chest, or difficulty concentrating. But the specifics are genuinely uncertain.
The honest position: the research on health effects is mixed, and much of it involves exposures that are not comparable to a home project. Studies on wind turbine infrasound, for example, have produced inconsistent results, and researchers continue to debate the findings.
What is better established is that very high sound pressure levels at any frequency can damage hearing. That is a general principle of acoustics, not specific to infrasound. If you are building something designed to move a lot of air at high output, protect your hearing and be cautious with prolonged exposure.
Do not treat any of this as a reason to experiment casually with high-output low-frequency devices. The evidence on long-term effects is limited, and “limited evidence” is not the same as “safe.”
Why Do Viral Infrasound Projects Rarely Work?
Most viral “infrasound” builds fail for the same few reasons.
- They produce audible bass, not infrasound, and the creator cannot tell the difference without a microphone.
- The enclosure is too small to radiate low frequencies efficiently.
- They rely on vibration, which feels impressive but is not acoustic infrasound.
- They skip measurement entirely and assume success.
None of this means infrasound is fake. It is real, well documented, and used in fields like geophysics, where researchers monitor infrasound from volcanoes and earthquakes. The gap is between professional instrumentation and what a weekend project can realistically achieve.
If your goal is to understand infrasound, the most useful first step is not building anything. It is getting a microphone that can measure it. Everything else follows from there.
Frequently Asked Questions
Can a normal subwoofer produce infrasound?
It can produce a small amount of output below 20 Hz, but usually not efficiently or at useful levels. Reaching true infrasound typically requires large drivers, big enclosures, and significant amplifier power.
Do fans really create infrasound?
Large, slow-turning fans and HVAC equipment can produce low-frequency sound that sometimes extends into the infrasonic range. This is a real and measurable effect, not a myth.
Is infrasound harmful to your health?
The evidence on health effects is mixed and much of it is debated among researchers. Very high sound pressure levels at any frequency can damage hearing, so caution with high-output devices is reasonable.
Why can’t I hear the infrasound my device makes?
Human hearing generally fades out below 20 Hz, so infrasound is often felt rather than heard. Confirming it requires a microphone rated for that range and spectrum analysis software.
