Beatline

The research

What each of these is actually worth

We include these binaural beats and sounds because people like them, not because we are selling you a mechanism. Here is what the research behind each one is actually worth.

We cite systematic reviews and meta-analyses where they exist, and name the individual trials where they do not. Where a study undercuts us, it is listed here too.

These describe what the research found, not how confident we are. Masking is settled physics on mixed trials. Binaural beats show a medium-sized effect across many studies that disagree with each other. Neither is a treatment, and we say so on every one.

Binaural beats

Medium-sized effect

Play one tone in your left ear and a slightly different tone in your right, and you perceive a third rhythm that is present in neither. Pooled across 22 studies the effect on anxiety, attention and memory is medium-sized and consistent. Reviews of anxiety specifically find it beats silence and beats noise-cancelling headphones.

Three beat rates in this app have a study behind that specific rate. A 3 Hz beat increased delta activity and lengthened deep sleep. A 6 Hz beat increased theta activity, including the frontal-midline theta associated with focused attention. A 15 Hz beat improved verbal working memory. Each is one experiment, not a settled result.

Two honest caveats. The trials disagree with each other a great deal, so the average hides a wide spread, and at least one large study found binaural beats made a task harder rather than easier. And the mechanism is still being pinned down: the largest review found eight of fourteen studies contradicted the entrainment hypothesis, so a beat at a given rate does not reliably drive the brain to that rate.

What that rests on

  • Garcia-Argibay, Santed & Reales, 2019. Psychological Research

    Studied
    22 studies · 35 effect sizes
    Found
    g = 0.45 (medium)
    Weight
    Consistent across outcomes

  • Jirakittayakorn & Wongsawat, 2018. Frontiers in Human Neuroscience

    Studied
    3 Hz beat during sleep
    Found
    More delta activity; longer stage N3
    Weight
    Small experiment; not an insomnia trial

  • Jirakittayakorn & Wongsawat, 2017. Frontiers in Neuroscience

    Studied
    6 Hz beat on a 250 Hz carrier
    Found
    More theta, including frontal-midline theta
    Weight
    An EEG resemblance, not the state itself

  • Beauchene et al., 2017. Journal of Neural Engineering

    Studied
    15 Hz beat · verbal working memory
    Found
    Better accuracy; changed cortical connectivity
    Weight
    Small; cognitive findings inconsistent elsewhere

  • Ingendoh, Posny & Heine, 2023. PLOS ONE

    Studied
    14 studies of EEG entrainment
    Found
    5 supported entrainment, 8 contradicted it, 1 mixed
    Weight
    Entrainment is not reliably reproduced

  • Xiong et al., 2025. Complementary Therapies in Medicine

    Studied
    14 trials · n = 1,047
    Found
    SMD −1.38 on anxiety (large)
    Weight
    I² = 91.6% - extreme inconsistency

  • Baseanu et al., 2024. Applied Sciences

    Studied
    12 studies · anxiety and depression
    Found
    Better than silence and than noise-cancelling
    Weight
    Systematic review; no pooled estimate

  • Melnichuk, Cooper & Hawk, 2025. Scientific Reports

    Studied
    80 students · within-subjects crossover
    Found
    Gamma beats improved attention; EEG confirmed entrainment
    Weight
    Varied by carrier and masking; no effect on vigilance decline

  • Ingendoh, Posny & Heine, 2023. PLoS One

    Studied
    15 EEG studies
    Found
    Entrainment inconsistent across studies
    Weight
    Superseded in part by later parametric work

Isochronic tones

Barely studied

A single tone switched rapidly on and off, rather than two tones offset between your ears. Because the pulsing is in the sound itself, it works on a speaker, which binaural beats cannot do.

It is also the thinnest evidence in this app. The largest review of this area covered seventeen studies, and only two of them used isochronic tones. We include them because they are the one option that works without headphones, not because the research is there.

What that rests on

  • Ingendoh, Posny & Heine, 2023. PLoS One

    Studied
    2 of 17 studies used isochronic tones
    Found
    Too few studies to pool
    Weight
    Entrainment “inconclusive at best” overall

  • Chaieb, Wilpert, Reber & Fell, 2015. Frontiers in Psychiatry

    Studied
    Narrative review of auditory beat stimulation
    Found
    Effects reported, mechanisms unresolved
    Weight
    Not a meta-analysis; no pooled estimate

Solfeggio and 432 Hz

The benefit is not the tuning

Two small trials compared 432 Hz against standard 440 Hz tuning. In the larger one, anxiety fell in every group - including the nurses who simply took a normal break without any music at all.

That is the clearest result here: the calm is real, and the tuning is not what caused it. Claims that these frequencies repair cells or alter DNA have nothing behind them at all.

What that rests on

  • Calamassi & Pomponi, 2019. Explore

    Studied
    Crossover pilot, double-blind
    Found
    Small heart-rate difference
    Weight
    Pilot; authors asked for larger trials
    Caveat
    A corrigendum was published in 2020.

  • Calamassi et al., 2022. Acta Biomedica

    Studied
    54 nurses · 3 arms
    Found
    Anxiety fell in all arms, including no music
    Weight
    No significant difference between arms

  • de Witte et al., 2020. Health Psychology Review

    Studied
    104 RCTs · n = 9,617
    Found
    Music reduces stress
    Weight
    Explains the effect without reference to tuning

Beat rates we are still unsure about

Exploratory, not established

Some beat rates in this app rest on a single exploratory study rather than a controlled experiment. They are here because they are widely used and harmless to try, not because the research is in.

A 0.25 Hz beat shortened the time to reach slow-wave sleep - in daytime naps, which is not the same as a night of sleep. A 40 Hz beat has been explored for attention and memory, and 40 Hz reliably produces a measurable response in the auditory system, but whether that changes how you think is unresolved. Rates around 7 Hz and 16 Hz have been tested and did NOT produce the EEG changes predicted, which we would rather tell you than leave out.

What that rests on

  • Sharpe, Mahmud, Kaiser & Chen, 2020. Brain Informatics

    Studied
    40 Hz gamma entrainment
    Found
    Possible effects on mood, memory and cognition
    Weight
    Exploratory pilot; not a protocol

  • Goodin et al., 2012. Reported in Ingendoh et al. 2023

    Studied
    7 Hz theta and 16 Hz beta vs control
    Found
    No frequency-specific increase in EEG power
    Weight
    Direct evidence against these two rates

  • Lopez-Caballero & Escera, 2017. Frontiers in Human Neuroscience

    Studied
    Binaural beats across several rates
    Found
    Failed to enhance EEG power or emotional arousal
    Weight
    A null result, reported as one

Nature sounds

Medium-sized effect

A recording of moving water, played on a loop. It is the one sound in this app that is not generated on your device, and it works the same way noise does: a steady wash of sound raises the level at which a sudden noise stands out.

Reviews of nature sound do find better sleep and lower stress, and the effect is consistent enough to state plainly. Two honest limits. The trials are mostly small, and they rarely separate the sound from the act of lying still with your eyes closed for twenty minutes - which is the same confound the 432 Hz research ran into. Nothing here says water is better than the noise colours a few rows up.

What that rests on

  • Ratcliffe, 2021. Frontiers in Psychology

    Studied
    Review of natural sound and restoration
    Found
    Consistent stress and attention benefits
    Weight
    Mostly small samples; mechanisms unresolved

  • Buxton et al., 2021. PNAS

    Studied
    18 studies · meta-analysis
    Found
    Improved health and positive affect
    Weight
    Water sounds strongest; heterogeneous designs

Noise masking

Well evidenced

Steady broadband noise raises the threshold at which a sudden sound becomes audible, so the door closing downstairs stops waking you. This is the least mystical thing in the app and the best understood.

One caveat we would rather state than bury: almost all of this research was done in hospital wards and intensive care, or with infants. Very little of it tested healthy adults in their own bedrooms.

What that rests on

  • Ding et al., 2025. Sleep Medicine

    Studied
    12 RCTs · n = 1,301
    Found
    Sleep quality improved
    Weight
    Varies by age group and setting

  • Khandelwal et al., 2025. Sleep Medicine: X

    Studied
    7 RCTs · n = 496 · hospitalised adults
    Found
    Sleep efficiency improved
    Weight
    Small trials; well tolerated

This app is for relaxation and focus. It does not treat, diagnose, or cure any condition. If sleep or anxiety is affecting your life, speak to a doctor rather than an app.