Ultrasound

For other meanings of "ultrasound" or "ultrasonic", see ultrasound (disambiguation). A baby in its mother's womb, viewed in a sonogram (brightness scan) A baby, aged 29 weeks, in a "3D ultrasound" Ultrasound is sound with a frequency greater than the upper limit of human hearing, this limit being approximately 20 kilohertz (20,000 hertz). Ability to hear ultrasound Some animals, such as dogs, dolphins, bats, and mice have an upper limit that is greater than that of the huma ...