Distribution and strength of sound in the human head

With the progress of the R&D of medical technology, ultrasound has been widely used in the treatment of various diseases. However, the details of sound field in a human head acoustically excited are still not very clear. In this work, we have revealed the dependency of intracranial sound field and skull stress on the location and frequency of the excitation, and on the head size by the FEM. The low-frequency ultrasound (<100 kHz) can well penetrate into the brain, and MHz ultrasound almost cannot penetrate into the brain. Ultrasonic energy tends to exist near the inner surface of the skull in the frequency range for ultrasonic therapies (500 kHz?2.5MHz). As the head size decreases, the ultrasonic energy goes deeper into the brain, and intracranial sound pressure increases sharply when the head size is less than half of the standard one.