Sleepyland Research
Browse accepted, evidence-led guides by topic. Medication, supplement-safety, and other higher-risk guides awaiting qualified review stay out of this archive.
Drafted by an AI agent and checked against the linked sources by a separate Codex AI reviewer; no human clinical review is claimed.
18 articles
Evening screens combine light, arousal, and stolen time. Blue-blocking glasses filter very differently, and the latest objective meta-analysis found no significant sleep benefit. A screen-free wind-down remains a reasonable low-cost experiment.
Light matters; glasses trials remain small and inconsistent
The goal is not to force thoughts away. Offload specific tasks, give worries a next action, stop clock-checking, and reduce the struggle around sleep. These techniques fit the cognitive logic of CBT-I.
Small direct trials plus strong CBT-I principles
Noise, nature sounds, music, earplugs, and silence solve different problems. The useful choice starts with what is keeping you awake, not with a universal ranking.
No universal winner; evidence varies by sound and problem
A pitch, a binaural difference, an EEG rhythm, and a noise spectrum can all be labeled in hertz. They are not interchangeable, and no single audible frequency is proven to cause sleep.
Frequency terms are real; single-Hz sleep claims are unproven
Masking does not erase sound. It changes audibility by adding energy near the frequencies and moments that carry the unwanted signal, while reducing contrast against the room's baseline.
Acoustics established; sleep benefit depends on the disturbance
Eight hours is a useful planning number, not a biological pass-fail line. Adult guidance says at least seven hours regularly, while experiments show why six can feel easier than it performs.
Seven-plus is guidance, not an eight-hour law
Contemporary forager studies find shorter, flexible, environmentally timed sleep rather than one pristine ancestral pattern. The useful lesson is about context, not copying a schedule.
Field evidence is diverse, ecological, and easy to overread
The first night in a new place is often lighter and more fragmented. Brain-vigilance studies explain part of it, but hotel noise, temperature, travel timing, and expectation still matter.
A real laboratory effect, not a complete hotel diagnosis
Morning outdoor light can strengthen an earlier circadian signal, especially when evenings are dimmer. The effect depends on biological timing, intensity, duration, spectrum, season, and prior light.
Strong clock mechanism; no universal minutes prescription
There is no universal best sound for focus. The useful choice depends on whether you are masking speech, supporting a repetitive task, reading language, or simply trying to make a session easier to begin.
Effects depend on listener, task, and sound
Three 2026 studies reached different answers: one found better self-reported sleep in older adults, another found less REM with pink noise, and a small traffic-noise pilot found selective masking benefits.
Evidence mixed; effects depend on the problem and protocol
There is no evidence-based universal slider percentage, decibel target, or bedside distance. A better setup starts with the noise you are solving, measures where your head rests, and uses the lowest level that changes the interruption.
Practical setup; no universal bedroom level
Masking adds sound, earplugs reduce sound at the ear, and active cancellation creates an opposing signal near the ear. Choosing well starts by naming the operation—not buying three products that solve different problems.
Mechanisms clear; direct sleep comparisons limited
A fan combines several experiences that search results often collapse into “white noise”: broadband airflow, mechanical tones, cooling, moving air, and a learned bedtime cue. The sound may help, but the closest direct home study did not find a significant sleep benefit.
Plausible mechanisms; direct sleep benefit unproven
The colors are engineering descriptions, not different medicines. Their spectral slopes change what you hear, what they mask, and how much volume feels comfortable.
Physics established; sleep superiority unproven
Ocean sound combines masking, slow energy changes, natural variation, and learned meaning. Those mechanisms are plausible; direct proof of better sleep in healthy adults is still limited.
Relaxation evidence stronger than sleep evidence
The sleepy passenger effect has names: motion-induced drowsiness, vestibular stimulation, whole-body vibration, and—in a stronger form—sopite syndrome. Sound is only one part of it.
Physical-motion mechanism supported
A steady cabin rumble and an aircraft passing over a bedroom are acoustically and psychologically different. One can become a familiar masker; the other is an intermittent sleep disruption.
Plausible masking and cue; no direct proof