How Much Do People with Sensory Hypersensitivity Suffer Outdoors — A Gap Not Found in Prior Research

This note is a deep dive into H1 of the 4 research hypotheses（このサイトの記事）.

Through comprehensive review of prior research, one clear gap emerged.

Urban environment research using wearable devices (GPS×heart rate×accelerometer) and research on sensory hypersensitivity/misophonia do not intersect at all.

This absence was re-checked on 2026-09-03 against Europe PMC using two search strategies. "(misophonia OR 'sensory hypersensitivity' OR 'sensory over-responsivity') AND (outdoor OR urban OR 'built environment') AND (wearable OR 'heart rate variability' OR electrodermal OR ambulatory)" returns 39 records; "(autism OR autistic OR 'sensory processing') AND 'ecological momentary assessment' AND (noise OR sound OR acoustic)" returns 313. Neither set contains a study that measured physiological responses in sensory-hypersensitive people while they moved through an outdoor urban environment. This is an absence within what these searches reach, not a claim to have exhausted the world's literature.

Research dealing with urban sound environments is biased toward fixed-point observation (stationary microphones) or laboratory experiments (sound presentation in soundproof rooms). Even for general citizens, few studies have measured "how much stress people experience in real-time while walking." For people with sensory hypersensitivity, the searches above found none.

Three fields are unaware of each other.

1. Wearable urban researchers (information engineering, urban planning) are unaware of the concepts of sensory hypersensitivity and misophonia. Their research targets "average responses of general citizens," with a tendency to exclude outliers.
2. Sensory hypersensitivity researchers (psychology, auditory science) conduct research within laboratory experimental paradigms. Japanese research by Sakuma, Matsui and others also centers on questionnaire surveys and indoor acoustic measurements.
3. Urban noise policy officials only look at time-averaged dB values. Individual sensory characteristics don't enter the judgment that "this road is below standard values, so there's no problem."

The research value of the Quiet Town Project lies at the intersection of these three domains.

Before claiming it's completely zero, let's confirm the closest research.

Kanjo et al. (2017) NotiMind research tracked urban pedestrians' emotional states in real-time by combining smartphone sensors and wearable devices. The approach of integrating GPS location information, acceleration, ambient sound levels, and heart rate variability provides direct insights for this project's technical design. However, the subjects were general citizens, and no stratified analysis by sensory characteristics was performed.

MacLennan et al. (2022) surveyed 49 autistic adults online in a mixed-methods study, combining quantitative results with analysis of the participants' own descriptions of their everyday sensory experiences. The study matters because it covers hyporeactivity and sensory seeking alongside hyperreactivity, and spans domains including vision. But it is retrospective self-report: it carries neither in-the-moment physiological data nor any measurement of the outdoor environment.

In other words, research on "urban outdoor×during movement×physiological data" and research on "sensory hypersensitivity×daily life×first-person account" each exist separately. The searches above turned up no study combining the two.

People with sensory hypersensitivity and misophonia tendencies show significantly higher physiological stress responses (heart rate variability, galvanic skin response) compared to general citizens during urban outdoor movement, which constrains their frequency of going out and route selection.

Participant Design: Two-group comparison between 15-20 adults with sensory hypersensitivity (self-identifying with ASD/misophonia) and 15-20 neurotypical adults matched for age and gender. Assuming Cohen's d=0.8 (large effect size), reaching 80% power at α=0.05 would require 26 participants per group (two-sided t-test). The 15-20 given here is a target set by what is feasible to run, and at that size the power is only 0.6-0.7. Degree of sensory hypersensitivity quantified using Glasgow Sensory Questionnaire (GSQ) and Amsterdam Misophonia Scale (A-MISO-S), also used as continuous variables in analysis.

Measurement Protocol:

• Walking the same route (approximately 2km route in Bunkyo Ward including main roads, residential areas, and parks)
• Continuous recording of heart rate variability (HRV) and electrodermal activity (EDA) with wearable sensors
• Simultaneous noise level recording with calibrated smartphone-mounted microphone
• Subjective stress recorded via smartphone EMA on 5-point scale (separating misophonia reactions, light stress, vibration stress)
• Cross-analysis by time period (morning rush, noon, evening, night) × route
• 8 sessions total per participant: 4 time periods × 2 repetitions each

Ethical Considerations: Since targeting people with sensory hypersensitivity, the research itself could become a stress source. Design allows interruption at any time, post-research debriefing, and referral to specialists as needed. Ethics review committee application planned for University of Tokyo or University of Tsukuba.

Zhang et al. (2020) paired GPS-equipped phones with portable noise sensors in Guangzhou, China, recording both the noise where participants actually were and the annoyance they reported at that moment. Measuring outdoors while people move is the closest existing method to this project's design. But subjects were general citizens only, with no stratified analysis of sensory hypersensitivity. Applying this method to people with sensory hypersensitivity forms the core of the Quiet Town Project's Phase 1.

If the hypothesis is supported, evidence would support the claim that "people with sensory hypersensitivity are canaries that first detect urban design flaws." Personal subjective suffering would be converted into the objective language of physiological data. Policymakers could redefine noise not as a "nuisance problem" but as a "health problem."

WHO's (2018) Environmental Noise Guidelines recommend keeping annual average road traffic noise exposure below 53dB(A)[1]. That recommendation rests on systematic reviews of the relationship between noise exposure and cardiovascular disease, effects on sleep, and cognitive impairment in children. However, this evidence targets general citizens, and the threshold at which people with sensory hypersensitivity experience health effects remains unknown. This research is an attempt to show that threshold with actual measurement data.

Another significance is extending the concept of "universal design" to sound environments. "Acoustic universal design" equivalent to tactile paving blocks for the visually impaired or slopes for wheelchair users has not yet been systematized. Data from people with sensory hypersensitivity would serve as foundational material for deriving those design standards.

References

Environmental Noise Guidelines for the European Region — World Health Organization (WHO) (2018). WHO Regional Office for Europe

NotiMind: Utilizing Responses to Smart Phone Notifications as Affective Sensors — Kanjo, E., Kuss, D. J., & Ang, C. S. (2017). IEEE Access, 5, 22023-22035

In Our Own Words: The Complex Sensory Experiences of Autistic Adults — MacLennan, K., O'Brien, S., & Tavassoli, T. (2022). Journal of Autism and Developmental Disorders, 52(7), 3061-3075

Geographic Ecological Momentary Assessment (GEMA) of environmental noise annoyance: the influence of activity context and the daily acoustic environment — Zhang, X., Zhou, S., Kwan, M.-P., Su, L., & Lu, J. (2020). International Journal of Health Geographics, 19, 50

聴覚過敏と暮らしの音環境 — 佐久間哲哉 (2021). Journal of the Acoustical Society of Japan (日本音響学会誌), 77(5), 296-301