After her late afternoon class, Sue and a friend leave campus and navigate the sidewalks and intersections surrounding the university that are congested with students, office workers, and traffic, all eager to get home. Listening to the environment around her, she can readily distinguish the sounds of cars, trucks, construction equipment, and the voices of other pedestrians that form the din of background sounds. Each of these sounds contributes to the complex variations in air pressure that press on our eardrums and which is the basis of hearing. She walks seemingly effortlessly while engaged in conversation with her classmate. Sue looks intently at her friend's face as the surrounding noise gets louder and her friend speaks louder trying to be heard over the noise at the street crossing. Distracted by the conversation and the effort of attending to her friends’ story, Sue begins to step into the intersection, but is alerted by a car horn and turns to her left to see an approaching car. Having safely navigated the intersection without falling and walking along the busy sidewalk, passing businesses and patrons seated at the sidewalk cafes, Sue hears someone call her name from one of the cafés. Even in the presence of background noise, the sound of her name immediately drew her attention and she shifts her gaze to the approximate location of the speaker.