Brainwave Entrainment During Emergence

The investigators will compare whether there is a significant difference in the time required for general anesthesia recovery according to application of the binaural sound after surgery.

After entering the operating room, electrocardiogram, pulse oxygen saturation, blood pressure meter, and sedline are attached to start monitoring vital signs and patient state index (PSI). propofol and the remifentanil continuous infusion device is connected as close as possible to the catheter insertion site. Anesthesia is induced with total intravenous anesthesia (4 ng/mL of Remifentanil, 4 mg/mL of propofol). Rocuronium is administered after checking the patient's unconsciousness. When appropriate neuromuscular blocking is reached, tracheal intubation is performed. The anesthesia maintenance is performed to keep stable vital sign and PSI between 25 and 50. End-tidal carbon dioxide is controlled to be between 30 mmHg and 40 mmHg.

When the pneumoperitoneum ends, the propofol concentration is recorded (T0). The anesthesiologist in charge of anesthesia puts headphones on the patient and plays the allocated file. The allocated file is named the screening number. Depending on the allocated group, the audio file is binaural sound for the experimental group, and a silent file for the control group.

The anesthesiologist cannot know group allocation, since the length and size of files are the same. Thereafter, the target of PSI is to be between 40 and 50. If the Psi increases above 50, increase the propofol concentration by 0.5 mg/mL and record it. Train of four counts keep between 1 to 3 (moderate block). When the operation is ended, stop anesthetics administration, and record the time (T1). At the same time, the investigators reverse neuromuscular blocking using sugammadex (2mg/ kg).

When the anesthesiologist starts waking the patient up, call the patient's name (unify into "OOO, open your eyes."). The anesthesiologist lightly tap the patient's shoulder and avoid excessive sound or stimulation.

Record the time (T2) when the PSI reaches 50, the time when the patient opens eyes (T3), and the time (T4) when the extubation of endotracheal tube was done. T3-T1 is the time it took the patient to open his eyes (primary end point). Write the effect site concentration of propofol and remifentanil recorded for each time points.

The patient's sedline EEG data from the end of pneumoperitoneum until the patient's exit operating room is collected as raw data. The patient's blood pressure and heart rate are measured at each time points. The investigators evaluate sedation and agitation of the patients using Ramsay Sedation Scale.

In the post-anesthesia care unit, pain score (NRS 0-10), postoperative nausea vomiting, medication, and length of stay are investigated.

Eligibility Criteria:
Inclusion Criteria:

* Patients between 19 and 50 years of age who are scheduled to undergo laparoscopic salpingo-oophorectomy/ ovarian cystectomy
* Intellectual level to understand the procedures of the clinical trial
* Physical status classification of the American Society of Anesthesiology (ASA) 1-2 grades

Exclusion Criteria:

* Patients with hearing loss or using hearing aids
* Patients who have been given narcotic painkillers or sedative drugs within a week.
* Alcohol-dependent or drug-dependent patients
* Patients with drug hypersensitivity to anesthetics
* Patients with arrhythmia, cardiovascular disease, impaired heart function, decreased circulatory blood flow
* Patients with liver failure
* Patients with other major medical or psychological disorder that will affect the treatment response
* Patients with claustrophobia or anxiety disorder
* Patients with organic brain disorders or other conditions that cannot be properly measured by PSI
* Patients who have been newly diagnosed with myocardial infarction, cerebral ischemic seizure, stroke, clinically significant coronary artery disease, or have undergone percutaneous carotid coronary dilatation or coronary bypass treatment within 6 months
* Patients with a history of epilepsy or seizures
* Patients with acute angle glaucoma
* Patients who deemed unsuitable for this clinical trial