It’s spooky season and the allure of horror movies has many of us cowering behind pillows, but have you ever noticed how some sounds seem to scare us way more than others? According to Jodi Sasaki-Miraglia, AuD (Doctor of Audiology) and Director of Professional Education Programs for Widex USA, there’s a science to the art of frightening noises.

Known as non-linear sounds, they defy our expectations of what is coming next and are something we’ve evolved to fear because – outside of the safety of horror movies – they’ve often meant something bad is about to happen. As Sasaki-Miraglia told IFLScience, there’s even been research into the way non-linear sounds can enhance cinema.

What are non-linear sounds?

Non-linear sounds are sound waves characterized by their exceptionally high amplitude and significantly greater volume when compared to other types of sounds. These sounds often contain abrupt frequency shifts, non-standard harmonies, or elements of chaos and noise. Many of us have experienced non-linear sounds in music, where parts of the music may be atonal or have dissonant characteristics causing our attention or mood to shift almost immediately.

Why have we evolved to fear them?

Our brains have evolved to recognize the abnormality in these non-linear sounds, enabling us to swiftly react to potential danger or distress. In the field of audiology, we’ve seen this human trait in action, known as the “acoustic startle reflex,” which occurs in milliseconds. The acoustic startle reflex can be observed even in newborns with normal auditory processing. 

The brain itself doesn’t know what’s going on until after we’ve reacted, manifesting as a fundamental survival mechanism. As you can imagine, our ancestors had reason to fear non-linear sounds that extend beyond the normal capacity of the vocal cords, such as the growl of a bear, the warning barks of your dog when there is danger around, or human screams.

What kind of fear response is typically triggered by non-linear sounds?

Research suggests that when exposed to non-linear sounds, such as loud and abrupt noises or discordant, chaotic sounds, the brain and body can react with a surge of adrenaline and cortisol, along with rapid breathing, a physiological response to fear. Moreover, the heightened adrenaline flow elevates heart rate and causes blood vessels to dilate.

How are they used in TV and film?

From the suspenseful theme of Jaws to the piercing violins in Psycho, film composers have the remarkable ability to evoke fear using just a few straightforward musical chords. They achieve this by amplifying unusual harmonies and manipulating frequencies, which allows the music to trigger primal fear responses encoded in our brains.

In a study, researchers conducted an analysis of over 100 soundtracks spanning across four genres: adventure, horror, drama, and war. They found that non-linear sounds, which add depth and intensity to the viewing experience, were prevalent in all these genres. However, their presence was particularly pronounced in horror and drama. 

For instance, whether it's a suspenseful moment just before a zombie attack or an emotionally charged scene where a couple is parting ways, non-linear sounds contribute to the overall appeal of the visuals. A classic example of this is the iconic T. rex roar in the movie Jurassic Park (1993), which was created by blending various animal sounds, such as a baby elephant, a growling tiger, and an alligator, to produce a truly terrifying effect.

Are there other examples of ways our hearing has evolved to enable us to better detect threats?

Relying on our ability to hear is crucial for our personal safety. Often, we can hear a potential threat before we can see it, or in some cases, when it might not even be visible at all. Good hearing plays a vital role in safeguarding our well-being, especially in situations like driving, walking in the dark and hearing “noises” nearby, responding to alarms for fire or intruders, or simply being aware of someone approaching us.

Additionally, our hearing needs to be balanced for us to determine the direction from which a sound originates. When one ear has significantly better hearing than the other, it becomes challenging to pinpoint the source of a sound or judge its distance accurately. In cases of imbalanced hearing, such as hearing loss in only one ear, the ability to perceive sound direction is compromised, posing safety risks like crossing a busy street. 

Thankfully modern prescription hearing aids can successfully help anyone who experiences a decrease in hearing or challenges listening to noise, and can restore balanced hearing, enabling wearers to hear everything around them in milliseconds. 

Widex, for whom Sasaki-Miraglia is Director of Professional Education Programs, has its Moment Sheer hearing aids, for example, with a unique program called PureSound powered by ZeroDelay processing that gives users the ability to experience sound around them naturally in less than 1 millisecond. This allows the user to experience the world, movies, and music the way it was intended, naturally. 

With modern hearing tech, users can experience those zombie sounds from movies as they were intended, and they can jump, laugh, and be a part of life again.