Smart earbuds that listen to your heart could lull you to sleep

Copied word for word from the study's registry entry, so the wording is the study team's rather than ours.

Inclusion Criteria * Aged 18 to 55 years (inclusive). * Able to understand the study protocol and voluntarily sign the informed consent form. * Meets the diagnostic criteria for chronic insomnia disorder according to the International Classification of Sleep Disorders, Third Edition (ICSD-3) or DSM-5. * Duration of insomnia symptoms is greater than 3 months but less than 2 years. * Insomnia Severity Index (ISI) total score \> 8 (indicating mild or greater clinical insomnia). * Currently drug-free status: No use of any prescription or over-the-counter medications that affect sleep (including sedatives, hypnotics, antidepressants, antihistamines, or traditional Chinese medicine sleep aids) for at least 2 weeks (or more than 5 drug half-lives) prior to enrollment. * Owns a smartphone and is capable of operating mobile applications to complete electronic questionnaires. * Willing and able to tolerate wearing earplugs or earbuds during sleep. Exclusion Criteria * Comorbid primary sleep disorders: Diagnosed via screening (STOP-Bang questionnaire) or polysomnography (PSG) with moderate-to-severe obstructive sleep apnea (OSA, defined as Apnea-Hypopnea Index $\\ge$ 15), narcolepsy, periodic limb movement disorder (PLMD), or other sleep disorders that could interfere with sleep quality assessments. * Severe psychiatric or psychological conditions: A Patient Health Questionnaire (PHQ-9) score \> 10 or a Generalized Anxiety Disorder scale (GAD-7) score \> 10. * History of schizophrenia, bipolar disorder, major depressive disorder, or active suicidal ideation. * Active substance abuse or dependence: History of alcohol abuse (exceeding 14 standard drinks per week) or illicit drug use within the past 3 months. * Comorbid somatic medical conditions: Severe or unstable physical illnesses (e.g., severe heart failure, malignant tumors, chronic pain) or neurological disorders known to impair sleep monitoring accuracy. * Active ear diseases, ear canal discharge, structural abnormalities, or a history of related otologic surgeries that prevent or restrict earbud placement. * Known history of hypersensitivity or allergic reactions to silicone or plastic materials. * Disruptive lifestyle factors: Current engagement in shift work schedules or travel across more than 3 time zones within 2 weeks prior to study entry. * Inability to provide independent informed consent or successfully complete cognitive testing due to profound language or cognitive barriers.