30 minutes before entering the operating room, the anxiety score is evaluated using a visual analogue scale (VAS) score, and stereo headphones, which can transmit binaural beat, are put on. According to a computer-generated assignment table, subjects are divided into an experimental group and a control group.

Binaural beat is applied to the experimental group for 20 minutes, and a silent state is applied to the control group for 20 minutes. After entering the operating room, electrocardiogram, pulse oxymetry, non-invasive blood pressure monitor, and sensor for depth of anesthsia are attached. Before induction of anesthesia, the anxiety score is evaluated on a VAS, again.

For anesthesia induction, propofol is administered at a rate of 10 mg every 15 seconds over 5 seconds. Assess the amount of propofol administered until the response to voice ("Open your eyes.") is absent, the subject's eyelash reflex disappears, and the PSI reaches below 50. Discontinue propofol injection when all three assessments (unresponsiveness to voice, loss of eyelash reflexes, Patient Sate Index (PSI) ≤ 50) become positive.

30 minutes before entering the operating room, anxiety is evaluated on a VAS score (0-100mm, a ruler without scale) and stereo headphones, which can transmit binaural beat, are put on. A third party unrelated to the experiment sees the randomization table and applies binaural sound to the experimental group and silent state (silent sound file) to the control group for 20 minutes.

The sound generator is a smartphone device, which is hung on the transport bed. The volume is set to a level corresponding to 60dB.

After entering the operating room, start monitoring vital signs and depth of anesthesia (PSI) by attaching an electrocardiogram, pulse oxymetry, non-invasive blood pressure monitor, and sedline. Prepare by connecting a 3-way at the most proximal part of the intravenous cannula. After changing the volume to 0, take off the headphones, and evaluate the anxiety score using VAS.

Preoxygenation with oxygen 8L/min is sufficient, and in order to reduce venous pain caused by propofol injection, 1% lidocaine 50mg is pre-administrated. For anesthesia induction, 10mg propofol is administered every 15 seconds for 5 seconds. Assess the amount and time of propofol administered until the response to the voice ("Open your eyes.") is absent, the patient's eyelash reflex disappears, and the PSI reaches below 50. Propofol is administered until all three evaluations (no response to voice, loss of eyelash reflexes, PSI ≤ 50) are positive. After that, propofol is not administered. During anesthesia induction, the concentration of the inhaled anesthetic is adjusted so that Psi is between 25-50, and the anesthesia process is the same for both groups.

Continuously monitor blood pressure, pulse, and Psi, and record the MAC value of the inhaled anesthetic immediately after tracheal intubation, vital signs, and Psi.

The raw data of EEG is stored through the Sedline sensor and additionally analyzed and evaluated. The primary endpoint is the dose of propofol administered until the response to the voice ("Open your eyes.") is absent

Inclusion Criteria:

• Adult patients aged 20-50 who require general anesthesia
• Patients who are able to provide written consent to participate in the clinical trial, to understand the procedure of this clinical trial, and to fill out the questionnaire appropriately
• Patients with ASA physical status classification 1-2
• Patients weighing from 50 kg to 80 kg

Exclusion Criteria:

• Patients with hearing loss or using hearing aids
• Patients who received narcotic analgesics or sedative drugs within 1 week
• Patients with alcohol or drug dependence
• Patients with drug hypersensitivity to propofol
• Patients with arrhythmia, cardiovascular disease, and decreased heart function
• Patients with liver failure
• Patients who are judged to be inappropriate for this clinical trial according to the opinions of investigators