Vibroacoustics, Helmholtz resonance and ghosts - OH MY

23rd October 2021. Reading Time: 12 minutes General, Paranormal Theories, Stuff paranormal investigators need to know. 2682 page views. 0 comments.

What is just a sound to one person, could be a poltergeist to another! How does sound physically affect a person? Can it make us believe we are being haunted? Can it also heal us?

Sound is one of those areas that a lot of those interested in the paranormal take notice of.  Depending on where you sit on the fence, you either think sound can help aid your research, or it can literally explain something that goes bump in the night.  Maybe like me you think it is a little bit of both.  What we will agree on though is how much sound does really play a part in how a person perceives what is happening around them.  There is a lot of talk about poltergeists, but not much said about false poltergeists - those which turned out to be something not paranormal at all.  The culprit often has something to do with vibroacoustics.

Vibroacoustic Phenomena

Vibroacoustics by definition is the study of vibration and sound combined to influence physiology.  In other words, how do certain sounds physically impact a person?  While it is commonly used within the field of sound healing, we cannot deny the effect that low-level frequency noise (LFN) can have on a person.  On the surface, what is just a sound to one person, could be a poltergeist to another!  

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Helmholtz resonance

Helmholtz resonance is described as the phenomenon of air resonance in a cavity.  The easiest way to describe it is the sound that happens when you blow across the top of a glass bottle.  In old buildings or even your own home, you can imagine how this could potentially cause some confusion on a windy night.  It could even be a great way to fake a haunting as some disgruntled workers demonstrated.

A room with an open window or door can also act as a Helmholtz resonator. When turbulent airflow passes through an opening in the room, it excites Helmholtz resonance. The natural frequency of Helmholtz resonance depends on the room’s volume, thickness of the walls, and area of the opening. If this value falls within the range of infrasound (below 20 Hz), it can cause creepy sounds in the audible range — perhaps leading to a suspected poltergeist.

Helmholtz resonance can be excited by sound waves propagating from an internal or external noise source. For example, thunder can reverberate in small rooms, which can be perceived as something more malicious than weather. The Sound & Vibrations article mentions a building that was rumored to be haunted. In actuality, the only thing haunting the building was revenge. The workers who built the apartment were scammed by the owner who hired them. To get revenge, the workers embedded empty glass bottles in the building’s roof. The bottles acted as Helmholtz resonators and wind passing through their openings at night caused tenants to hear roaring sounds at a frequency of 100 Hz.

Walking into an old building on a cold windy night is the kind of thing paranormal investigators (myself included) love to do.  Often it is a building that we may not be as familiar with.  It would be very easy for an open door or slightly open window to intensify nerves and excitable feelings that people there are already feeling.  Let's remember they are there because they want to witness, document or just feel something paranormal.  The low whistle through a window or even a ventilation duct can be just enough for someone to think they are not in the room alone.

It seems even in the comfort of our own home we can jump to the conclusion something paranormal is happening.  During lockdowns, there was an increase in the number of people who reported paranormal happenings going on in their own homes.  In at least some of these cases, it turned out to be a case of people becoming more familiar with the noises their house makes.  A friend of mine for example felt late at night like they were being watched.  It seemed to be the same time every night.  One night when I was over there, I felt it too.  With a little inspection we found out the culprit was not a ghost lurking in the kitchen, it was the fridge.  At around 10 pm at night it would kick over with a very low hum.  This LFN is also known as infrasound and is one of the more common ways LFN can make us think we are being haunted.


The human ear can hear sound from around 20-20000hz. Infrasound is described as a low-frequency sound that is below 20hz. Hz stands for hertz and 1 Hz is the equivalent to 1 vibration per second. Quite a lot of people can hear well below 20hz so to some it may be inaudible and not to others depending on how low the frequency is and what your personal threshold is. It is actually thought some people can hear as low as 12Hz.

Infrasound is a very low-level frequency of sound.  Animals such as Giraffes and Elephants use it to communicate across their large herds over long distances. Before natural disasters, animals seem to flee the area before the disasters hits. It is believed that they are picking up on the infrasound causing them to become fearful and flee. Volcanos emit infrasound when they erupt and meteors also give off infrasound while travelling through space. Infrasound can be detected by a microphone so scientists use it to track animals, monitor volcanos and follow the flight paths of meteors in spaces. 

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The fear frequency

Whilst it is a frequency that the human ear may not be hearing, our bodies are certainly feeling it. It is also nicknamed the fear frequency or ghost frequency for this very reason. Scientific testing has shown us that when exposed to infrasound, people have reported feeling anxiety, extreme levels of sorrow, chills, fear, blurry vision, hallucinations and people have spotted what they describe as apparitions. Infrasound itself causes the eyes to vibrate which causes this disturbance in our vision. There is a very famous article ‘The Ghost in the Machine’ published in the Journal for The Society of Physical Research which covers the story of Vic Tandy who worked in a college laboratory. Workers in the lab including Tandy reported paranormal activity.  The lab itself gained a reputation as being haunted. 

The company’s business was in the design of anaesthetic or intensive-care, life
support equipment so there was always some piece of equipment wheezing away in a
corner. When V.T. heard suggestions that the lab was haunted this was the first thing
he thought could be behind it and paid little attention. One morning however none of
the equipment was turned on and V.T. arrived just as the cleaner was leaving
obviously distressed that she had seen something. As a hard nosed engineer V.T. put
it down to the wild cats, wild other furry things, moving pressure hoses (as the
pressure fluctuates, flexible hoses sometimes move) or some sort of lighting effect.
As time went on V.T. noticed one or two other odd events. There was a feeling of
depression, occasionally a cold shiver, and on one occasion a colleague sitting at the
desk turned to say something to V.T. thinking he was by his side. The colleague was
surprised when V.T. was found to be at the other end of the room. There was a
growing level of discomfort but the workers were all busy and paid it little attention.
That is until V.T. was working on his own one night after everyone else had left. As
he sat at the desk writing he began to feel increasingly uncomfortable. He was
sweating but cold and the feeling of depression was noticeable. The cats were moving
around and the groans and creaks from what was now a deserted factory were
"spooky", but there was also something else. It was as though something was in the
room with V.T. There was no way into the lab without walking past the desk where
V.T. was working. He looked around and even checked the gas bottles to be sure there
was not a leak into the room. There were oxygen and carbon dioxide bottles and
occasionally the staff would work with anaesthetic agents, all of which could cause all
sorts of problems if handled inappropriately. All of these checked out fine so V.T.
went to get a cup of coffee and returned to the desk. As he was writing he became
aware that he was being watched, and a figure slowly emerged to his left. It was
indistinct and on the periphery of his vision but it moved as V.T. would expect a
person to. The apparition was grey and made no sound. The hair was standing up on
V.T.’s neck and there was a distinct chill in the room. As V.T. recalls, "It would not
be unreasonable to suggest I was terrified". V.T. was unable to see any detail and
finally built up the courage to turn and face the thing. As he turned the apparition
faded and disappeared. There was absolutely no evidence to support what he had seen
so he decided he must be me cracking up and went home.

The Ghost in the Machine Published in the Journal of the Society for Psychical Research Vol.62, No 851 April 1998

By sheer luck one day, Tandy realised that the foil on a metal blade was vibrating at the same time he felt like he wasn't alone. After lots of investigation and tests, it was found that there was a fan transmitting infrasound at around 19Hz that induced these feelings. When this fan was turned off, all activity stopped completely.

Here is a fun fact .... composers use infrasound frequencies in horror movie soundtracks to help evoke the feeling of dread and pure fear while watching a horror movie! It is even said to be used as a method of torture because of the adverse effect it has on the body.  Put simply, it makes us feel like we are not alone!

Vibroacoustics and sound healing

While we have looked at the ways that sound can make us think something paranormal is happening, vibroacoustics are also used as a form of healing through sound.

The concept of sound healing is traced back to Ancient Greece where music was used to treat different mental disorders. Culturally, sound has always played a significant part.  Nomadic shaman, the Tibetan Lama, Christian, Islamic, Hindu, African or Jewish priest, musician or cantor to name a few, Whether it is chanting, drumming or other means, sound has been used throughout time to balance a person's chakras and even heighten a person's state of consciousness.  Most Ancient cultures used sound to heal in different ways.  As the world developed, the concept of sound healing didn't quite disappear, but it was no longer a common method used to heal anymore - likely because we now had medicine etc.

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In the spiritual community, you will hear the word vibration mentioned a lot.  Even when discussing the spirit world, people believe that different vibrations can attract different kinds of energy etc.  It would come as no surprise that vibration can affect the human body.  We know that infrasound and the right frequency can make us feel paranoid.  It is why horror movies use certain notes in their soundtracks, as your body has a physical reaction. 

In 1982, Olav Skille defined vibroacoustic therapy (VAT) as the use of sinusoidal, low-frequency (30-120Hz), rhythmical sound-pressure waves mixed with music for therapeutic purposes. It was thought that "low-frequency sound massage” would assist in the reduction of pain and other stress-related symptoms. This type of therapy usually involves not just wearing headphones, but often lying on special mats where your body can 'feel' the vibration.  

Sound and the paranormal

Sound is not just something that you hear, it is something you can feel as well.  We don't see it, but we feel it.  A lot of people would describe paranormal phenomena in the same way.  So while it could be sound that makes us feel that way, could it also be something else? We know that frequency plays some sort of part in the paranormal. EVP relies on certain frequencies. Infrasound can not only make us feel like we are experiencing something paranormal, some believe it can help unlock some sort of residual energy. Energy and frequency are all around us. Consciousness itself is defined as being aware. There is a long debate over what happens to us when we die. While our physical body dies, many believe that our consciousness lives on. When we are communicating with what we believe to be spirits, it is possible we are communicating with some kind of consciousness. What if the person was actually still alive? Mysticism teaches that this is possible. Astral travel suggests that is possible. Is our consciousness limited to our physical body? Then of course there are the abilities that many suggest we all have within us. Potentially we could all be capable of having some sort of psychical ability, we just need to learn how to tap into it.  Many spiritual pages claim that the frequency of 7.8hz Theta waves can help to unlock ESP ability and that Alpha waves at 8.3hz can help stimulate a person's psychic ability.  So while many argue that LFN makes us feel like something paranormal is happening, do these frequencies actually allow us to experience it by tapping into those abilities?

When exploring sound when it comes to the paranormal and more specifically our own experiences, we know that we can replicate a paranormal experience just by listening to the right sound file.  So how do we know if what is happening is due to sound or if it is something else?  Maybe we aren't supposed to know the answers, or maybe sound is the clue to getting closer to them?

If you want to find the secrets of the Universe, think in terms of energy, frequency and vibration.

Nikola Tesla


Vinokur, R.. (2016). Things that go bump in the night: The physics of "false" poltergeists. 50. 14-18. 

Vinokur, Roman. (2004). Infrasonic sound pressure in dwellings at the Helmholtz resonance actuated by environmental noise and vibration. Applied Acoustics. 65. 143-151. 10.1016/S0003-682X(03)00117-8.

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