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Musical Acoustics

  1. Dec 14, 2003 #1
    My final is in two days and I am clueless. My professor issued a series of sample test questions. Any help would be appreciated. Thanks.

    1. What is a frequency spectrum? Why is a spectrum special if it contains only frequencies belonging to a harmonic series?

    2. What is a natural mode? Why is it important? What determines which modes of a system are vibrating? How can one excite a particular mode preferentially? (Know examples from various instrument families) Why is it nice if the natural modes of some system have frequencies in a harmonic series?

    3. What are the natural modes of bars, plates, strings, open and closed cylindrical air columns, conical air columns? Where possible, know formulas for the frequencies of these modes.

    4. What is the actual motion of a string that is struck, plucked, or bowed? How are these motions related to natural mode motions? What determines which modes are excited in each case? What is the role of a violin soundbox, or a piano soundboard?

    5. What are the relations between pressure and displacement nodes in a standing wave of air in a pipe? What is a flow-controlled valve? What is a pressure-controlled valve? What is the difference between a hard and a soft reed? What is a lip reed? What is the function of finger holes in a woodwind, and of register keys (vent holes)? What are characteristics of valves on a brass instrument? What is the purpose of the bell on a woodwind or brass instrument?

    6. When singing a sustained tone, what are the roles of the vocal cords and the vocal tract? What are formants? What are some particular problems of singers?

    7. In the case of each instrument that produces a sustained tone, how is energy provided to the primary vibrator? How does the primary vibrator control the times at which energy is provided?

    8. In room acoustics, what is meant by direct sound and reflected sound? What is the precedence effect? What is reverberation time and how is it related to absorption of sound by walls? What are desirable amounts of reverberation? What is a simple formula for estimating reverberation times?

    9. What is the place theory of pitch perception? What does pattern recognition play a role in pitch perception? What are sum and difference tones? What are some situations in which nonlinearities are important? What are critical bands of hearing, and why are they important?

    10. What kind of frequency relation defines a particular pitch interval? What are just intervals and equal-tempered intervals? Why are they not the same? Why are both used? What is the cents scale? How can Hall's tile mosaics represent particular tuning schemes?
  2. jcsd
  3. Dec 15, 2003 #2


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    This seems to cover pretty much an entire semester's worth of material on acoustics. Did you just sleep through the entire semester, or what? No one here is just going to answer all your finals questions for you; nor is anyone going to attempt to teach you a semester's worth of acoustics on a web forum. At the very least, you need to show us the work you've done on the problems, and where you got stuck.

    - Warren
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