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Unformatted text preview: Physics 1240 Hall Chapter 6 Notes 1 Focus questions and learning goals Chapter 6 focus questions: 1. How does the human ear work? 2. How do the ear’s physical properties affect our perception of sound? Chapter 6 learning goals. After studying this chapter, you should be able to: 1. Explain the physical structure and function of the major parts of the ear (outer, middle, and inner). We’re not interested in memorizing part names, but you should describe and explain the physical effect on perception of sound caused by features of the ear. 2. Explain what determines the frequencies we’re most sensitive to. 3. Explain physically how you can tell high pitches from low ones. 4. Explain the function and/or consequences of anatomical features such as bumps and wiggles on the outer ear, the length of the ear canal, the large relative size of eardrum to oval window, and the change in thickness of the basilar membrane as it runs through the cochlea. 5. Explain the connection between physical variables (intensity, frequency, and waveform) and perceptual variables (loudness, pitch, timbre). Which matter the most, and what can alter the perception? 6. Describe what the Fletcher-Munson diagram tells us about the relation between pitch, SIL, and perceived loudness. Use this diagram to make predictions about how various sounds (e.g., recordings) will change in character when you crank up or down the volume. 7. Explain what Just Noticeable Difference (JND) refers to, and use graphs of JND to make predictions, for example which sounds you could distinguish, and what changes would be needed to distinguish them. 2 Intro to human ears This chapter has a lot of cool stuff in it. We’re not going to cover it all in lecture. But if you’re interested in the connection of physics and physiology and psychology, I encourage you to read it! I’ll talk about the ear in class, at a level slightly simpler than section 6.1. You don’t need to memorize the names of these various parts (unless you’re into that kind of thing); what I want you to take away is a sense of the physical purpose of a few key elements, as outlined below 1 Physics 1240 Chapter 6 notes 2.1 The outer ear The outer ear is the channel and structures that help bring sound waves to the eardrum. This part of the ear ends at the eardrum. The eardrum is a thin membrane that vibrates when there is excess (or under-) pressure on the outside. (The inside, i.e., the middle ear, is enough separated from the outer ear that changing room air pressure causes the eardrum to vibrate. ) 2.2 The middle ear The middle ear connects to the outside world through the Eustachian tube to your throat. (That’s why swallowing, or holding your nose and blowing, can help equalize the pressure in your inner ear and the outside world when you’re flying. When would you want to blow your nose, or chew gum, on takeoff, or on landing? Why?) The middle ear has this awesome collection of little “levers”: three bones (called the hammer, anvil, and stirrup, colloquially) which transfer the...
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This note was uploaded on 08/24/2010 for the course PHYS 1240 taught by Professor Holland,murray during the Spring '08 term at Colorado.
- Spring '08