A measurement for sound frequency, the less hertz, the less high pitched, the more hertz, the more high pitched. The average hearing range in hertz is 20 to 20,000 hertz, but it varies due to age, the younger you are, the more you hear. Most animals have a larger hearing range to us.
Little kid: Ow, can you hear that sound with lots of hertz? Its really painful!
Old man: Nope, can't hear anything, there is no sound with lots of hertz.