Chapter 10 Overview
Hearing in the Environment
Imagine it’s a dark summer night and you’re sitting next to a campfire (at right; click the links to hear each sound). Suddenly, you hear a bullfrog start croaking behind you. Then a cricket chirps just in front of you and on your right. Then, as luck would have it, it starts to rain. These four sounds all enter your ears through the same paths (via the auditory canals), yet somehow you separate the sounds, identify each one’s source, and figure out where each source is located. (If you get tired of hearing the sounds in the background, you can click the images or links above to stop them.)
This chapter is about how we accomplish these tasks, using auditory information to learn about our environment. First we learn how we determine where sounds are coming from using heuristics described in the activity on Auditory Localization Cues. Next we see how the auditory system processes complex sounds, especially sounds that include a fundamental frequency along with other harmonic frequencies that are multiples of the fundamental. The activity on The Missing-Fundamental Effect demonstrates how the auditory system bases perception on the fundamental even if this frequency is not actually present in the sound wave. The third activity demonstrates an easy-to-hear but hard-to-define sound quality called Timbre, and the essay discusses the effects of Reverberations on sound perception.
The fourth activity covers some of the Gestalt-like “rules” that we use to separate sounds coming from multiple sources (e.g., the fire, frog, cricket, and raindrops in our example here), a process called Auditory Stream Segregation. Finally, the Continuity and Restoration Effects activity explores the auditory analog of filling in behind occluded parts of a visual image.
Once you’ve read the chapter in the textbook and done the activities here, use the study aids (Study Questions, Flashcards, and Chapter Summary) to review.