Why do humans have two ears? How do the properties of sound help with directional hearing? Students learn about directional hearing and how our brains determine the direction of sounds by the difference in time between arrival of sound waves at our right and left ears. Student pairs use experimental set-ups that include the headset portions of stethoscopes to investigate directional hearing by testing each other's ability to identify the direction from which sounds originate.

Students follow the steps of the engineering design process to create their own ear trumpet devices (used before modern-day hearing aids), including testing them with a set of reproducible sounds. They learn to recognize different pitches, and see how engineers must test designs and materials to achieve the best amplifying properties.

With the challenge to program computers to mimic the human reaction after touching a hot object, students program LEGO® robots to "react" and move back quickly once their touch sensors bump into something. By relating human senses to electronic sensors used in robots, students see the similarities between the human brain and its engineering counterpart, the computer, and come to better understand the functioning of sensors in both applications. They apply an understanding of the human "stimulus-sensor-coordinator-effector-response" framework to logically understand human and robot actions.

Students gain a rigorous background in the primary human "sensors," as preparation for comparing them to some electronic equivalents in the associated activity. A review of human vision, hearing, smell, taste and touch, including the anatomies and operational principles, is delivered through a PowerPoint® presentation. Students learn the concept of "stimulus-sensor-coordinator-effector-response" to describe the human and electronic sensory processes. Student pairs use blindfolds, paper towels and small candies in a taste/smell sensory exercise. They take pre/post quizzes and watch two short online videos. Concepts are further strengthened by conducting the associated activity the following day, during which they learn about electronic touch, light, sound and ultrasonic sensors and then "see" sound waves while using microphones connected to computers running (free) Audacity® software.