A trailer that promised pure auditory terror, Undertone is a Canadian supernatural horror film marketed as one of the scariest movies you will ever hear. To put that claim to the test, FearScale recruited a subject who suffers from phonophobia, the fear of loud or sudden noises.

If any film could strike the right chord, this would be it. Could a movie built on sound design alone truly make her heart race, or would it fall flat and fade into background noise?

SYNOPSIS:

The host of a popular paranormal podcast becomes haunted by terrifying recordings mysteriously sent her way.

FearScale™ Methodology

FearScale measures how frightening a horror film truly is by monitoring real-time heart rate data from human test subjects during controlled viewing sessions. Each subject’s baseline resting heart rate is recorded prior to the film, allowing us to identify meaningful spikes caused by tension, dread, shock, or sustained unease.

Heart rate increases are tracked throughout the runtime and correlated with specific scenes to determine when fear responses occur, and how intense they are. This data-driven approach helps separate genuine physiological reactions from subjective opinions or post-viewing impressions.

Because fear is personal, FearScale does not claim universal results. Instead, each session offers an objective snapshot of how a film impacts the human body under consistent conditions, providing a unique, measurable lens on horror.

Viewing Conditions:

Our test subject watched Undertone at home, seated on her couch with a single dim lamp casting soft light across the room. The space was quiet and free of distractions, allowing the film’s sound design to blend with the natural creaks and ambiance of her surroundings.

Where We Monitored: Home

Test Subject: Jennifer

Age: 34

Gender: Female

Fears: Phonophobia or the fear of loud noises

Resting Baseline HR: 61-64bpm

Walking HR: 80-85bpm

ANALYSIS:

From the opening moments, Undertone sets an unsettling tone. A chilling blend of soft singing layered with heavy breathing immediately put our subject on edge. It was an effective start, subtle yet sinister, raising her heart rate and tuning her senses to every whisper and creak.

However, that tension doesn’t always sustain. A lengthy, one-sided conversation between the main podcast host and her unseen partner causes the film’s momentum to dip. With only two actors carrying the narrative, the film leans heavily on dialogue and atmosphere, sometimes to a fault.

As the story unfolds, eerie voice recordings begin to surface. While this could risk becoming monotonous, the film manages to deliver several genuinely haunting moments. These sequences create a low, persistent hum of dread, suggesting something malevolent lurking just beneath the surface. Even simple actions, like walking up a staircase, carry a faint but effective tension. Not quite a scream-inducing spike, but enough to leave a lingering echo of unease.

Around the 33-minute mark, the paranormal elements intensify. Our subject’s heart rate climbed from 68BPM to 82BPM over the course of ten minutes, a gradual rise, but a respectable one. She became increasingly invested in the mystery as it unraveled.

Unfortunately, once the initial novelty of the sound design wears off, the pacing becomes noticeably slow. By the third act, while the volume increases and the chaos builds, the film still struggles to push into higher FearScale territory. Despite a few sharp notes, it never quite crescendos into full-blown terror. The tension dissipates too often, making it difficult to sustain that edge-of-your-seat feeling.

CONCLUSION:

Undertone delivers a slow-burning, atmospheric experience that doesn’t fully capitalize on its intriguing premise. While it has moments that resonate, it ultimately never amplifies its scares enough to match its bold marketing.

For viewers looking to maximize the FearScale experience, headphones and complete darkness are essential, otherwise, much of the film’s impact gets lost in translation.

If you’re craving horror that truly sounds off, consider films like Insidious or Pontypool, which hit harder, louder, and with far more intensity.

FearScale Viewing Environment Note:

To fully experience Undertone, your environment matters just as much as the film itself. This is not a movie to casually watch with distractions.

For the best results:
• Watch in complete darkness, no ambient light
• Use high-quality headphones to capture every whisper and distortion
• Eliminate background noise entirely
• Sit close to the screen to stay visually and psychologically engaged

FEAR CALORIE BURN:

One ear of corn contains around 155 calories, while Undertone has the potential to burn off 189.

More FearScale Results

• Insidious: (Heart Rate Breakdown)

• PontyPool: (Watch Trailer)

How many Fear Calories did you burn watching Undertone (2026) ?  Let us know in the comments below or on Instagram, and Facebook