A standard model head for testing. European helmet testing uses EN 960 headforms sized by circumference from 445 to 645 mm (44.5 to 64.5 cm), smooth domes with no face or ears. For smart head-worn devices, IEEE P4115, the standard that would set the head shapes, became a project on 14 May 2026 and has no published text.

Designing devices for the human head

Q: How long does a head-worn device take to build?

Nuraleve s neuromodulation headband , built for clinical use in pain and addiction therapy, reached a pre-production prototype ready for clinical testing in under 12 months. TritonWear s swim tracker took 20 months from concept to certified mass production.

Designing for the head means holding a sensor in the right spot, on every head shape, comfortably, for hours. Here's what the head does to hardware, from earbuds to a brain-bleed scanner, and how we designed around it.

Kevin Bailey Founder and CEO · 12 min read

A handheld scanner built to find bleeding under the skull depends on holding its detectors at fixed distances on a curved, hair-covered scalp.¹

Earpieces in research labs already read brain activity, heart rate, blood oxygen and temperature.^2,3 In September 2024 the FDA authorized the first over-the-counter hearing aid software, for use with compatible Apple AirPods Pro.⁴ In May 2026 the standards body IEEE approved a project to standardize the head shapes used to analyse smart head-worn devices: glasses, helmets, earphones and masks.⁵

The head carries an unusual number of signals,^2,6 and it's the hardest place I know to put electronics. The surface is curved, covered in hair, sensitive to heat and weight, and a different shape on every person. Put a sensor a little off and the data is wrong. Make the band tight enough to hold it and nobody wears it.

We've designed nine devices for the head in the last five years, and three in the five years before. The figure shows where six of the devices we designed meet the head. What follows is what the head demanded of them, one challenge at a time.

Where six devices we designed meet the head Each number marks where a device meets the head, with what it reads or delivers there and a constraint its portfolio page describes.

Neurovine headband

Forehead, four mapped scalp sites (Fpz, Fp1, AF7 and AF8) plus two ear references. EEG, four channels, 200 readings a second each.

Hold four forehead sites across adult head sizes, with fabric windows and a one-handed adjuster.
ArcheOptix scanner

Scalp, pressed on by hand. Near-infrared light, detectors at about 15, 27 and 42 mm.

Keep the detector distance fixed and the light out, through curved, hair-covered scalp.
TritonWear pod

Back of the swimmer's head. Motion, orientation, depth and heart rate.

Go on the right way around with no instruction, because the swimmer cannot see it.
Calibre breath tracker

A mask on a headband strap. CO₂, O₂, pressure and humidity in the breath.

Fit every face with one size while the wearer's own breath condenses on the sensors.
Smart Audio Awareness Glasses

Frame rims, in the client's patented concept; what we built is a standalone demonstrator. The direction of a sound, shown by LEDs in the wearer's peripheral vision.

Fit the microphone array and live inference within the size and power limits of a head-mounted assistive device.
Electrode-Retaining Headband

Two tDCS electrode sites on the 10-20 map. Transcranial stimulation, delivered through sponges.

Even pressure, so the current never concentrates enough to burn the skin.

Source: Design 1st portfolio pages, captured 28 September and 1 October 2026. Drawing: Design 1st, from the data.

The seven sections below take those demands in order: where the sensor sits, which head shapes to fit, how much weight, heat and pressure people will wear, getting through hair, the radio rules close to the body, pairing, and the fake heads to test on first. The checklist at the end turns each one into a requirement.

On the head, choosing the sensor is the easy part

Where a sensor sits on the head decides what it measures, so most of the engineering goes into holding it there. Measuring brain activity with sensors is not new. What is new is doing it without distraction as we go about our daily lives, rather than immobile on a hospital gurney.

Most of the early product requirements drafts I review for a head-worn device start with the technology needs, talking in "channels" and the sample rate. Fit to head often gets one line near the end, and on the head that line decides more of the design acceptance and success than the sensor array performance does.

Clinical electroencephalography (EEG), which reads the brain's electrical activity through the scalp, has fixed sensor placement by one scheme since 1958.⁷ That scheme, the international 10-20 system, fixes each electrode at 10 or 20 per cent of the distances between landmarks on the skull.^7,8 In a clinic, someone finds those landmarks by hand and measures between them.⁸ A product has to do that on a stranger, at home.

Neurovine holds the map with fabric

The Neurovine headband, built to monitor brain activity during concussion recovery, does it in a clever way using fabric.⁹ A precision-cut fabric window holds each of its four dry (gel-free) electrodes on its mapped scalp site, and a strap adjuster, validated across adult head sizes, fits the band one-handed at a steady pressure.⁹

ArcheOptix holds each detector at a fixed distance

ArcheOptix set out to detect brain bleeds just under the skull at the point of care, without the wait for a hospital CT.¹ Its scanner is a handheld near-infrared instrument a clinician holds against the scalp.¹ With near-infrared light, the gap between the light source and the detector limits how deep a reading goes.^10,11 Light reaches substantially less than half that gap into the head, and adult cortex (the brain's outer layer) is commonly read across about 30 mm, through about 13 mm of scalp and skull.^10,11

ArcheOptix sets its detectors at three distances, roughly 15, 27 and 42 mm from its infrared source, and holds their alignment to under 1 mm.¹ The scalp is curved and hair-covered, so each detector rides a spring-loaded floating carrier that holds a fixed sensing distance while conforming as the head presses in.¹ Clinical-trial units were delivered first, then a production design ready for manufacture.¹

Cutaway of a generic near-infrared probe on the scalp, with detectors at rising distances from a light source and deeper light paths — Fig. 01 · A generic near-infrared probe, drawn to show the idea and no particular design. The farther a detector sits from the light source, the deeper its light path runs. The farthest detector is in orange. Schematic. Not to scale. Illustration: Design 1st.

Europe's standard helmet test head has no face and no ears

Helmet labs testing to Europe's EN 960 use faceless, earless heads, and IEEE P4115, the project to standardize head shapes for smart glasses, earphones and masks, was approved only on 14 May 2026.^5,12

Those helmet headforms (test heads) are smooth domes in graded sizes, 44.5 to 64.5 cm around in 1 cm steps, under the European standard EN 960:2006.¹² That already covers the 5th to the 95th percentile of the US Army's 2012 survey: 53.2 to 59.7 cm around in women and 54.8 to 60.1 cm in men.¹³ The sizes exist, but the test heads lack a face and ears.¹²

Fig. 02 · EN 960 helmet-test headforms are smooth domes in graded sizes, with no face or ears. The ear on the real head, in orange, is what they leave out. Illustration: Design 1st.

Military data miss civilian faces

The US workplace-safety agency NIOSH built new respirator fit panels because the old ones rested on 1967 and 1968 Air Force surveys, and military data don't represent the range of civilian faces.¹⁴ So the usual fit check, a prototype passed around five heads in the office, tells you even less.

Calibre Biometrics, whose mask tracks breath, started from an anthropometric (body-measurement) analysis of facial structures, then tested 3D prototypes on people to capture data on fit to face variations.¹⁵

The swimmer can't see the TritonWear pod

The TritonWear swim tracker shows what covering a real range takes. Its sensor pod rides on the back of a swimmer's head, where the swimmer can't see it, and its algorithm depends on where it lands.¹⁶ It had to fit youth swimmers, long hair and varied head shapes, which took three concept directions and fit testing before the form was locked.¹⁶ The production housing is shaped to go on the right way around with no instruction, and thousands have shipped.¹⁶

The evidence supports no universal weight limit for headsets

A 2026 review of comfort in virtual reality headsets by Zamora Alviarez and colleagues concluded that the evidence doesn't support universal limits for mass, temperature, pressure or interface geometry.¹⁷ For comfort, your own wear trials set the numbers for your device.¹⁷

What the research does offer is warnings. In a two-hour wear study, not everyone lasted the full session in a 500 g headset.¹⁸ For the least tolerant quarter, each added 33 g cost about 11 minutes of comfortable wear.¹⁸ Across five VR headsets, the air against the face warmed by an average of 7.8 °C in 45 minutes.¹⁹

Mass alone misleads, because fatigue tracks the torque at the neck as well.²⁰ US Army researchers write their preliminary helmet guidance as a weight moment, the weight times its distance from the head's pivot on the spine.²¹ Their figure is 134 N·cm for a 10 per cent drop in performance, about what 1 kg does when it sits 14 cm out from that pivot.²¹

Side view of a head wearing a headset, its centre of mass marked well forward of a pivot at the top of the neck — Fig. 03 · The same mass strains the neck more the farther its centre of mass sits from the top of the spine. The headset's centre of mass is in orange. Illustration: Design 1st.

Heat has a medical limit, and safe pressure is unknown

For a medical device, the line is IEC 60601-1.²² A part that touches the patient and isn't meant to heat should stay at or below 41 °C, with up to 43 °C allowed when risk management justifies it.^22,23 For pressure, the safe limit is unknown.²⁴ Ventilation masks chosen and fitted by experienced staff still exerted mean pressures of 47.6 to 91.9 mmHg on the bridge of the nose.²⁵ That is above 32 mmHg, the assumed capillary closing pressure, a figure traced to 1930 measurements.^24,25

Our favourite fix added weight to balance the device on the head, on purpose

The procedure a medical device developer brought us for tDCS (transcranial direct current stimulation, a therapy that sends a stimulating current through electrodes on the scalp) had barely changed in decades.²⁶ One person held the sponges in place while a second wrapped an elastic bandage over them.²⁶ The pressure has to be firm and even, so the current never concentrates enough to burn the skin.²⁶

On the Electrode-Retaining Headband, counterbalanced weights press the electrodes down, so nothing is cinched tight.²⁶ What used to need two people and a tape measure became a job for one, and every part of the system works with one hand.²⁶

Without gel, hair stands between a dry EEG electrode and the scalp

A typical human hair is 50 to 100 µm thick, and when matted to the scalp it forms a barrier to electrodes.^27,28

Magnified scalp cross-section: hair shafts thicker than the thin outer skin layer, with a dry electrode pin between them — Fig. 04 · A dry electrode pin among hair shafts, magnified. A typical hair is thicker than the outer skin layer, in orange. Not to scale. Illustration: Design 1st.

Wet electrodes get through with gel.²⁸ Without it, a dry electrode's impedance, its resistance to the signal, typically runs above 100 kΩ, more than 10 times that of a wet electrode, which sits under 10 kΩ.²⁸ Then the wearer moves. Motion artefacts, the electrical noise that movement adds to a recording, typically run at least 10 times the amplitude of the signal.^2,29

Neurovine's headband uses dry silver conductive-fabric pads at four forehead sites, held at a steady sensor-to-skin pressure, with signal quality and contact resistance covered in its bench testing.⁹ The forehead was chosen partly to stay clear of hair and partly for how the band goes on, and its two ear references, used as grounds, sit where hair is out of the way too.

Light and breath get in the way too

ArcheOptix designed a disposable scanning head, snapped on fresh for each patient, that seals against the scalp with a light shield and a flexible silicone bellows that keep ambient light off the sensors.¹ Calibre's enemy was the wearer's own breath, condensing on the CO₂, O₂, pressure and humidity sensors of a wearable breath tracker.¹⁵

The radio rules change 20 cm from your body

Under US rules, a transmitter designed for use within 20 cm of the body is a portable device, and unless its power sits under the exemption thresholds it's judged by the radio energy that human tissue absorbs.^30,31

That measure is the specific absorption rate (SAR), in watts per kilogram.³¹ The US rule counts the outer ear as an extremity, like a hand or a foot, at 4 W/kg over any 10 g.³¹ The rest of the head gets the stricter public limit of 1.6 W/kg over any 1 g, and Canada's RSS-102 Issue 6 sets the same figure for the head, neck and trunk.^31,32

For a module certified as a mobile device, the 20 cm line from the head is where its own certification stops covering the product.^30,33 A module certified on the assumption that people stay at least 20 cm away was assessed as a "mobile" device, the Federal Communications Commission (FCC) term for one used that far from the body.³³ In a headband, it sits within 20 cm, so the finished product is assessed as a portable device against the SAR limit, with a test unless its power sits under the FCC's exemption thresholds.^30,31

Fig. 05 · Inside 20 cm of the body, a transmitter is assessed as a portable device. The boundary is in orange. The same module on a stand sits outside it. Not to scale. Illustration: Design 1st.

Finding out late in the product development that your product needs to meet a special human body proximity, sensitivity, environment of use or chemical compatibility regulation can result in a much larger development budget for redesign as well as the substantial third-party regulation testing that was not planned for. Choose a development team that has a strong history in body-worn device development that passes the required regulatory tests and trials, on the way to market.

A swimmer's radio goes under on every stroke

On a swimmer, a TritonWear pod's Bluetooth link surfaces and submerges on every stroke.¹⁶ Its antenna was tuned through the housing plastics, and a high-density Bluetooth network serves more than 50 of those bursty links from a single coach's tablet at poolside.¹⁶

Neurovine's battery chemistry was chosen for the head

On Neurovine we tested alternative chemistries first, then had a manufacturer build a custom UL-certified battery in a chemistry chosen for safer operation near the head, with protection circuitry watching charge, current and heat.⁹

For risky commands, the FDA recommends a button press

The FDA's February 2026 cybersecurity guidance recommends that, where unauthenticated use could cause harm, a device should also require a physical action, such as a momentary switch, to authorize the session.³⁴

Neurovine's headband applies the same idea to pairing, the step that links two devices. It pairs only when someone presses its button.⁹

The first head your device meets should be a fake one

A test rig finds much of what goes wrong on the head before a person ever wears the product.

For Calibre's breath tracker, we designed a testbed of mannequin heads, bellows pumps and calibrated gas cylinders, built to verify the tracker's breath measurements for accuracy and repeatability.¹⁵ A calibration system used reference gases of 4 per cent CO₂ and 16 per cent O₂ to correct the variation between one unit and the next.¹⁵

A mannequin head on a test bench wearing a breath mask, with a hose to a bellows pump and a gas cylinder behind — Fig. 06 · A breath-measurement testbed: a mannequin head wearing a generic mask, in orange, a bellows pump and a gas cylinder. Illustration: Design 1st.

Neurovine's test head is fed known brain signals in the factory

Neurovine's three-stage factory test checks EEG accuracy against IEC 80601-2-26, the standard for the basic safety and essential performance of EEG equipment.^9,35 The last stage is a sample check that feeds known brain-signal patterns through the sensors on a test head.⁹

The glasses demonstrator's rig turns full circle

The Smart Audio Awareness Glasses began as a patented concept, an LED ring in the eyeglass rims that lights toward an arriving sound for people with hearing loss.³⁶ The custom-designed test rig rotated a microphone array through full 360° sweeps, hundreds of training samples a session, alongside a sound isolation chamber built for the project.³⁶ The direction model scored above 95 per cent accuracy across multiple independent test datasets, and independent testing of the demonstrator at the client replicated the findings.³⁶

Testing doesn't stop at the bench. Every TritonWear pod passes a production-line test equivalent to 30 m (98.4 ft) of water.¹⁶

The requirements checklist for a head-worn device

Each problem the head causes becomes a line in the requirements document, with an owner and a test to verify meeting the specification.

Head-worn device requirements

Where each sensor must sit, to what tolerance, named against a skull landmark or a 10-20 site.
Owner: human factors and mechanical; test it on headforms and on people who put it on without a mirror.
The head size/shape/hair range you'll fit, from which dataset, and whether one size or an adjuster covers the range chosen for the design to meet.
Owner: industrial design; test with fit trials at both ends of the range, long hair included.
How long it's worn, and the mass and centre of mass that allows.
Owner: industrial design, mechanical; test with timed wear trials, and log when each wearer first notices the device.
The highest temperature any skin-contact part may reach, and the standard that sets the limit.
Owner: mechanical, industrial design, electronics; test skin temperature during the longest session, and find ways to stay within the standard's limit.
Where contact pressure is applied, and how it stays even as the head moves.
Owner: industrial design, mechanical; test with pressure mapping on a headform and on people.
What can come between sensor and skin, whether hair, sweat, oil, breath, saline or light.
Owner: electronics, optics; test signal quality on worst-case hair, with movement and motion.
Whether the radio sits within 20 cm of the body.³⁰ If it does, it's assessed against the SAR limit, with a test unless its power sits under the exemption thresholds.³⁰
Owner: electronics; pre-test at a low-cost lab for potential success, test SAR at an accredited lab.³¹
The battery's chemistry, protection circuit and certification, at cell and at product level.
Owner: electronics; test the cell and battery to IEC 62133-2:2017 with Amendment 1:2021, the battery to UL 2054,^37,38 then the product to its own standard.
How it pairs, and what stops anyone else connecting.
Owner: firmware; test by pairing with a second phone in the room. NIST's Bluetooth guide says "Just Works" pairing, where the user accepts a connection without checking a code, should not be used for Bluetooth Low Energy.³⁹
The data rate, how lost packets are detected, and what runs on the device.
Owner: firmware; test streaming in the worst radio position.
The safety, performance and quality standards you'll design to, and which approvals you're treating as goals.
Owner: regulatory; map the test plan to the standards clause by clause.
How every unit is tested in production.
Owner: manufacturing NPI (new product introduction) and test; write the fixture or firmware test before design freeze.

Those are the head's seven demands, from where the sensor sits to the fake head it meets first. Write them into your requirements, and fit stops being the one line near the end.

Writing device requirements against a pilot date? Our free requirements tool drafts them from a description or a pitch deck and flags the level of certainty and what will need validating.

Head-worn device questions, answered

What can you measure from the head?

Brain activity, heart rate, blood oxygen, temperature, breathing and eye movement have all been read at the head or ear in published research.^2,3,6 Devices we designed add breath gases through a face mask, and motion, depth and heart rate at the back of a swimmer's head.^15,16

What are hearables?

Ear-worn devices that do more than play sound. Research hearables sense EEG, heart rate, blood oxygen and temperature.^2,6 Compared with other body parts, the ear stays relatively stable, though chewing and talking still move it.^6,40 In September 2024 the FDA authorized over-the-counter hearing aid software for use with compatible Apple AirPods Pro.⁴

Can you record EEG from the ear?

Yes, but ear EEG is more susceptible than scalp EEG to motion artefacts from jaw and head movements.^2,41 One 2025 review counted more than 250 papers on ear-based electrical sensing by August 2024, and a 2026 review by Channa and colleagues reports a shift toward wireless designs that process on the device.^6,41

What is an EEG headband?

A band that holds electrodes at fixed scalp sites and streams the signal to an app. Neurovine's headband reads four channels at four forehead sites, each at 200 readings a second.⁹

How heavy can a head-worn device be?

A 2026 review of virtual reality headsets found the evidence doesn't support a universal number.¹⁷ In a two-hour study, each added 33 g cost the least tolerant quarter of wearers about 11 minutes of comfortable wear.¹⁸

What is a headform?

A standard model head for testing. European helmet testing uses EN 960 headforms sized by circumference from 445 to 645 mm (44.5 to 64.5 cm), smooth domes with no face or ears.¹² For smart head-worn devices, IEEE P4115, the standard that would set the head shapes, became a project on 14 May 2026 and has no published text.⁵

Does a radio module certified at 20 cm cover a head-worn device?

No. Inside 20 cm it counts as a portable device, so the specific absorption rate (SAR) limit applies: in the US, 1.6 W/kg over any 1 g of tissue, with a test unless its power sits under the exemption thresholds.^30,31

How long does a head-worn device take to build?

Nuraleve's neuromodulation headband, built for clinical use in pain and addiction therapy, reached a pre-production prototype ready for clinical testing in under 12 months.⁴² TritonWear's swim tracker took 20 months from concept to certified mass production.¹⁶

Read next

Sources

Show all 42 sources

All read 1 October 2026.