DirecTone

A directional siren indicator for DHH drivers.

Industry: Product design, human-centered design
Tools: SolidWorks, KeyShot
Year: 2024
Experience: Human-centered design, rapid prototyping, user research, physical computing

About

A product render of the DirecTone device, a small round puck with four arrows on its face, one lit green.

For a semester-long group project, we designed a proof of concept assistive device to help deaf and hard-of-hearing drivers stay safe on the road. It detects emergency sirens and translates them into visual cues, showing the direction the sound is coming from. Through user research and iterative testing, we’re shaping it into an intuitive, inclusive concept that reduces stress and improves driver confidence.

*To ensure high-fidelity presentation, some project images have been refined using AI for resolution and clarity. Please note that no project concepts, CAD data, or design solutions were AI-generated*

Challenge

For drivers who have hearing disabilities, detecting the direction of an emergency vehicle can be challenging. With sirens granting you key context into the direction of the incoming emergency vehicle, missing this audible warning can lead to a delay in emergency response time and potential threat to those hard of hearing.

Four parties are thus affected by this:

the DHH driver

the emergency vehicle driver

the person in need of assistance

and other drivers on the road

With one product for one person, could we eliminate the effects of three other parties?

This problem calls attention to creating equitable situational awareness while driving, specifically amongst emergency vehicles

How might we design an assistive device that helps deaf drivers not only detect emergency vehicles before seeing them but also understand their direction quickly and intuitively?

User Research

We interviewed 4 drivers (3 hard-of-hearing, 1 hearing control) across age groups to understand:

Their current assistive tools.
Coping strategies for emergencies.
Feelings and stress levels when sirens occur.

Key Findings

Hearing aids alone are insufficient for spatial awareness.

Many rely on watching other drivers’ reactions.
Drivers want independent, clear, and intuitive alerts.

Early concept sketches exploring a vibrational mass and a small LED feedback device mounted near the windscreen.

Sketches of a steering wheel with embedded sensors and a top-view diagram showing the driver's location relative to an approaching emergency vehicle.

Sketches of a light emitting array on the dashboard and a vibration wrap for the steering wheel, annotated with how the vibration frequency would indicate distance and direction.

A line drawing of a car interior annotated with an RGB LED matrix for dynamic light patterns, steering wheel vibration, and radio frequency indication, mounted on the dash.

A line drawing of a rear-view mirror with a small round device hanging behind it, annotated with a 360 degree MEMS microphone array, driver's seat vibration, and LED array directional control.

We went through several ideations on how we should mount this device on a vehicle. Some included a steering wheel mount, a light indicator as a part of the steering wheel, a dashboard mount, and a stiff mount behind the rearview mirror.

We needed to think about where this device could sit that would not obstruct the vision of the driver, would be a universally accessible point, and would be most straightforward to understand.

A steering wheel option is not the most viable since it is constantly behind rotated so the directional element would be unreliable. A dash mount could work, but a lot of cars have differing anatomies.

Something that is consistent in all cars in the rearview mirror so we went with that mounting option. The mount would be stiff to prevent any swinging from motion.

A simple illustration of the device hanging from a rear-view mirror, showing a single upward arrow lit.

The device shown head on with a green beam projecting upward from it, illustrating the lit arrow pointing toward the direction of the siren.

The mount hangs behind the mirror, and the body charges over USB.

Design

While sound-recognition technology is a solved problem in the tech industry, the delivery of that information in a high-stress driving environment is not. Our study focused on the ergonomics of the rearview mirror placement and the cognitive load of the directional LED indicators.

The main limitation was the lack of an integrated acoustic sensor array to automate sound detection in real-world traffic. Future iterations would implement machine learning to isolate and classify emergency sirens amidst ambient road noise.

A six-panel storyboard: a hearing-impaired driver on the road, a fire truck appears, the seat vibrates after detecting the siren, the direction of the fire truck is displayed, the driver reacts and is more confident, and finally gives way to the truck. — Six frames, from the siren arriving to the lane being clear.

A laser-cut wooden puck with four arrows on its face, wired to an Arduino board on a workbench. — The first build, laser-cut and wired to a board.

The finished translucent prototype glowing amber, hanging in a car with its downward arrow lit white. — The finished body, hanging in the car with one arrow lit.

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