BEHIND ARC’S MECHANICAL CHIME
We’ve always admired the timeless appeal of analog clocks—but those harsh, old-school bell alarms? Not as much. When we set out to design Arc Alarm Clock, our goal was simple: create a calming wake-up experience. Little did we know, it would take 2.5 years of fine-tuning to get it just right. The result? A completely custom-engineered alarm mechanism, designed to wake you gently.
Below, we explore the intricate design of Arc’s mechanical chime, from how it gradually builds in intensity, to the scientifically chosen frequency that eases you into wakefulness.
WHAT IS THE CHIME?
Arc’s alarm uses an aluminum chime bar, struck several times over three minutes. The cadence and intensity gradually increase, gently waking you with a middle B note (B4).
Why B4?
At 493 Hz, this frequency was carefully chosen for its ability to wake you without causing anxiety.
For context, the frequency range of a crying baby (300-600 Hz) falls within the most sensitive range of human hearing, with higher pitches (above 500 Hz) sounding more urgent. At 493 Hz, B4 sits in the mid-range—making it easy to hear, but not overly alerting. This frequency is perceived as alerting without being jarring.
Why gradually build the alarm?
Research has shown that melodic alarms, particularly those with soothing tones, can help reduce morning grogginess, known as sleep inertia, which many experience upon waking. Harsh, jarring alarms tend to shock the system, leading to disorientation and impaired cognitive function for several hours. With this in mind, the Arc Alarm Clock’s chime was specifically designed to offer a more gradual, gentle wake-up experience.
The tempo of Arc’s chime, between 100-120 bpm, was carefully selected to match the natural rhythm that promotes calm arousal. This approach is rooted in studies showing that a structured, melodic sound can stimulate the brain without causing abrupt disturbances.
To further enhance this gradual wake-up, our musician in residence Ryan Bahm, employed sequential velocities to create a subtle, soothing pattern. This variability in sound prevents the alarm from becoming predictable, making it less likely for users to habituate to it, a key challenge in maintaining an effective wake-up alarm over time.
ONE CHIME, MULTIPLE TONES
Designing a custom chime bar was necessary because no standard commercial option could hit a B4 note and be short enough to fit within an alarm clock. To achieve this, we partnered with Eric Luakkanen, an acoustic engineer specializing in percussive beams. Eric's experience is rare and invaluable, as demonstrated in his work on 'Modeling and Tuning of Musical Percussive Beams.' Together, we crafted a custom chime bar design that sounds great and meets our stringent mechanical requirements.
Above: Illustration highlighting the vibration patterns “modes” of a chime bar with a uniform rectangular cross section (Source).
Overtones arise from secondary and tertiary vibrations, or "modes," in a chime bar. The primary mode generates the fundamental frequency when struck, while the other modes create overtones. The key to pleasant sound lies in the ratio of these overtones to the fundamental frequency. A harmonious ratio enhances the fundamental note, while an imbalanced ratio leads to dissonance and harsh ringing.
Every dimension of the bar, including length, width, and thickness, plays a crucial role in achieving the desired sound quality. We conducted hundreds of simulations to perfect a mechanical design that balanced sound harmony with our size constraints.
The development of the chime bar involved multiple design iterations and manufacturer feedback to achieve a scalable design. Remarkably, a mere 10-micron variation in thickness could detune the bar, a tolerance far too tight for mass production. One of the most difficult tasks was optimizing the bar to accommodate a more standard production tolerance while still meeting the sound requirements. Ultimately, we made six physical iterations before finalizing the design.
OUR LOW-TECH SOUND LAB
With all of these prototypes, we needed a place to test our iterations! We built a soundproof box for testing made from a repurposed shipping crate and lined with acoustic foam. This might seem low-tech compared to renting a recording studio, but scrappy solutions like this save a small team significant time and money.
Crafting Arc’s chime was a journey of precision and creativity, from tuning the perfect note to balancing every overtone. The result? A mechanical chime that gently wakes you up, without the jarring start of traditional alarms.
"Arc not only looks stylish in the bedroom, it’s completely changed my mornings. The sound bath-like chime wakes me gradually without the anxiety of a typical alarm clock. Plus it helps me keep my phone out of my bedroom."
— Mallory
Sources:
- McFarlane, S., Garcia, J., & Verhagen, D. (2020). Sound of music: How melodic alarms could reduce morning grogginess. RMIT University. Published in PLoS ONE, doi:10.1371/journal.pone.0215788.
- Bahm, R. Musician and Arc Alarm Clock Chime Composer.
- Luakkanen, E. Modeling and Tuning of Musical Percussive Beams.
