Shalini Nair
Chartered Accountant
We’ve all experienced the excitement of watching a horror/thriller movie in a theatre. The
goosebumps you feel in the anticipation of the next jump scare are just not the same as when
watching at home. Your heart races, your palms are cold and clammy, and your skin crawls;
everything just seems scarier when watching it on the big screen.
But have you wondered if this thrill is caused by the visuals and sound effects alone? Is there
some hidden factor which movie makers use to enhance the cinematic experience?
Infrasound is the category of sounds which are below the threshold of human hearing but can be felt as vibrations in the human body. These sound waves, even though inaudible, can create physical reactions such as anxiety, fear, and nausea. Some movies, particularly horror movies, use these to create an immersive experience for the audience.
Science behind the sound
Before delving into the effects of these sounds, it's important to understand more about the human auditory system. Human beings perceive sounds with pitch, but pitch is quantified in frequency. The higher the frequency at which the sound waves oscillate, the higher the pitch. The range for audible sounds for humans falls between 20 Hz to 20,000 Hz. Any sound below 20 Hz is categorized as Infra sounds. Some of the examples of Infrasound found in nature are the sound of very large waves, earthquakes, volcanic eruptions, etc. Even certain animals like elephants can perceive and communicate via infrasound. There is a scientific hypothesis that the ability to perceive infrasound helps animals presage natural calamities.
Movie magic
In movies such as A Quiet Place, The Conjuring 2 or even the latest Malayalam movie Manjummel Boys, producers have admitted using infrasound to create worry and fear while watching the movie. To produce infrasonic sound in a theater environment, specialized subwoofers are used that are designed to accurately produce low-frequency sounds. These subwoofers are typically much larger than regular speakers. These sounds, when passing through the human body, create vibrations, which in turn increases the cortisol level in the body. Cortisol is the hormone the body releases under stress, which causes physiological and psychological changes such as heart racing, goosebumps, anxiety and fright.
Other applications
Interestingly, infra sounds have also been linked with paranormal activities. Various studies have interpreted subsonic sound waves in areas which are generally considered haunted. Some countries even use acoustic devices for riot control and crowd management.
Infrasound is slowly creeping into our everyday lives without making a sound. From high tech
surround sound systems to cinema Dolby systems, sonic weapons to international nuclear
monitoring system.
Next time when you feel creeped out or scared watching movies, it may not be eerie piano
music, hushed footsteps, or ticking clocks. It might just be the sound you cannot hear.
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