We mentioned above that most people can hear sounds ranging In frequencies from 20 to 20,000 Hz. But sound waves can have higher or lower frequencies than this range, even though they cannot be detected by human ears. Many animals can detect frequencies outside of this range, and even for humans, non-audible sound waves can have technological uses. Sound waves with frequencies lower than 20 Hz are claied as Infrasound. Animals such as whales and elephants are known to communicate using infrasouncl, and earthquakes have been known to generate Infrasonic waves. Low-frequency waves tend to \"spread out\" from openings and travel "around" objects more easily than high- frequencv ones (a process known as 'diffraction"), so infrasound tends to travel for long distances. Sound waves with frequencies higher than 20,000 Hz are called ultrasound. Ultrasound is frequently used in medical imaging. Ultrasound scanners emit sound waves into the body, which reflect off of tissues and allow images to be Fon'ned. Bats and dolphins emit ultrasound signals and listen for their reflections, allowing them to navigate or locate prey without light. Imagine a hat that is hanging stationary. It emits an ultrasound pulse toward a moth, which is hovering stationary. The pulse travels toward the moth, reects off of it, and heads back toward the bat's ears. The total time elapsed from the emission of the pulse to being received by the bat's ears is 25.0 milliseconds (where 1 millisecond - 1 x 103 s}. How Far (in m) is the moth from the bat? Use a speed of sound 343 mfs. :lm