Students learn the decibel reading of various noises and why high-level readings damage hearing. Sound types and decibel readings are written on sheets of paper, and students arrange the sounds from the lowest to highest decibel levels. If available, a decibel meter can be used to measure sounds by students.

Students learn about sound and sound energy as they gather evidence that sound travels in waves. Teams work through five activity stations that provide different perspectives on how sound can be seen and felt. At one station, students observe oobleck (a shear-thickening fluid made of cornstarch and water) “dance” on a speaker as it interacts with sound waves (see Figure 1). At another station, the water or grain inside a petri dish placed on a speaker moves and make patterns, giving students a visual understanding of the wave properties of sound. At another station, students use objects of various materials and shapes (such as Styrofoam, paper, cardboard, foil) to amplify or distort the sound output of a homemade speaker (made from another TeachEngineering activity). At another station, students complete practice problems, drawing waves of varying amplitude and frequency. And at another station, they experiment with string (and guitar wire and stringed instruments, if available) to investigate how string tightness influences the plucked sound generated, and relate this sound to high/low frequency. A worksheet guides them through the five stations. Some or all of the stations may be included, depending on class size, resources and available instructors/aides, and this activity is ideal for an engineering family event.

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.