What is Infrasound?
Infrasound is sometimes categorized as low-frequency sound or signals that are lower than 20Hz in frequency. This also means that it is below the standard threshold of human hearing which is 20Hz – 20kHz.
Infrasound can occur naturally in the environment from such things as avalanches, lightning (thunder), calving of icebergs and earthquakes to name a few. Animals such as Whales and Elephants use infrasound to communicate over great distances. In the case of Whales, over hundreds of miles.
At greater sound pressure levels it is possible for humans to perceive infrasound through tactile vibrations throughout the body.
Why is Infrasound important to my Haunt or Escape Room?
As a haunt or escape room owner, Infrasound can be utilized to introduce a fantastic new experience to your guests. Sound in and of itself, is a medium that lends itself perfectly to the haunted and escape room industry. It can’t be seen, can be placed in almost any location, is easily manipulated and is one of the primary human senses to be impacted and interpreted by your guests.
When we start thinking of Infrasound, we can immediately open new ways of interacting with our customers. With Infrasound, it is now possible to add the sensation of touch or feeling to our environment without a physical prop or actor. In addition, there are studies that have shown that Infrasound can cause a sense of uneasiness and dread in a person as they are exposed to sound at very low frequencies.
So how does this work?
One client that we worked with had been toying with the idea of adding low frequencies to a particular area of their haunt. Using a bass amplifier, specific measurements of the hallway, and a quick calculation, gave us what we needed to implement the effect.
The setup went something like this.
We had a hallway of approximately 20 ft. in length.
Wavelength (Lambda) = Wave Velocity (v) / Frequency (f)
based on the speed of sound at sea level, and at 20 degrees Celsius or 72 degrees Fahrenheit
We calculated the wavelength at 56.5 Hz, meaning that it would repeat almost exactly over itself from the signal source (bass amp) from the wall 20ft away.
This in and of itself does a couple of different things.
- You are likely to get what’s called standing waves. These can cause sensations of volume level attenuation and amplification as you walk through a room. This is a very “odd” effect and can cause disorientation and some confusion as you walk through.
- At this low of a frequency (and lower of course) you begin to feel the sound, and at sufficient amplitude, the sense of uneasiness and dread begins to take place in some individuals. I will caution, however, that sound pressure levels should never exceed 90dB for exposure of 8 Hours or more. This is especially true for actors and individuals needing to be in proximity of amplified audio of this level for long durations.
What other options do I have for tactile audio?
Another great way to get your customers feeling the audio, is to implement what is called a transducer. Better known as a ButtKicker, these transducers utilize a moving piston that is activated by the input of low frequencies from your sound system.
Generally, the transducer (ButtKicker) is attached to an object (say a chair, wooden floor, desk, prop, etc.) and a sound signal is delivered to the ButtKicker to make it vibrate. Most often, the signal is 100Hz or lower and the ButtKicker only responds to those frequencies.
The advantage here is that you don’t have any sound waves traveling through a room to make this happen. This can be very convenient for Thunder, explosions, growls of your favorite creature prop, etc. By using a ButtKicker to vibrate a floor, you can now enhance, let’s say, Thunder and Lighting in a room and the vibration will flow through your guests giving them a one of a kind experience they won’t forget!
Below I’ve provided a couple of studies on the use of Infrasound and low frequencies and how they can effect people. As always, make sure to be safe, protect your hearing and that of your customers.
Thanks for reading!
Infrasound Linked to “Spooky” Effects
The Ghost in the Machine
Investigation of the Paranormal