Final Exam

Short answers (2 pts):

1. Define the following prefixes (e.g. femto = 10-15 ): centi deci micro mega milli giga
2. What is the speed of sound in air at normal temperature and pressure?
3. What happens to the speed of sound as the air temperature rises?
4. Air is a non-dispersive medium for sound waves. What does this mean?
5. Sound waves are longitudinal. What does this mean?
6. What is a standing wave?
7. What is simple harmonic motion? List two systems that exemplify this.
8. Define the phase of one sine wave with respect to another. Now state Ohm's Law.
9. State the principle of superposition of waves. How would our aural experience be modified if this were not true?
10. Define refraction. Explain why you can hear so clearly across a lake at night.
11. Which instruments of a marching band can you hear from around a corner? Why?
12. Define harmonic series.
13. State Fourier's theorem for periodic functions.
14. Why are temperaments necessary?
15. Describe an edgetone. What instruments make use of this principle?
16. What are the physical analogs to pitch, loudness and timbre?
17. In certain ranks of wooden organ pipes, the length decreases as one plays up the keyboard until at a certain point, the next pipe becomes almost twice the length of the previous one and it has a hole drilled half way up its length. Explain what is ha
18. Why are low piano strings tuned flat?

    Quantitative: (3 pts)

19. Draw a sine wave with frequency 100 Hz. Make sure the time axis is properly labeled.
20. A string of length 1m has fundamental frequency 50 Hz. What are the first 10 possible normal-mode frequencies that can sound if the string is plucked at 1/6th of its length?
21. The fundamental frequency of notes played on a piano range from 28 Hz to 4435 Hz. Suppose we pick out 34.4 Hz (about C#1) and 3440 Hz (about A7). What are the wavelengths of these two notes? How do these wavelengths compare to the lengths of the strings that produced them?
22. At 10 feet, the sound from a large speaker at a rock concert is causing you pain. How far away from the speaker do you need to move to get the sound intensity to decrease by a factor of 100? If the SIL at 10 ft is 120 dB, what is it after you have
23. An F horn has a fundamental at 43.7 Hz. If the instrument behaves like an open tube, how long must it be? Does the size of this number make sense?
24. If one flute plays a C at 60 dB and another plays a G at 60 dB, what is the SIL of the two instruments together? Hint: log10(2) = 0.3.

    Longer answers: (4 pts)

25. Write down how you would explain to your roommate the working of your ear.
26. Write down how you would explain to your roommate why the pitch of a moving ambulance is higher as it comes toward you and lower as it recedes.
27. Explain the process of digital sampling.
28. . Describe the ideal room for a small pipe organ like the one we visited. What are the acoustic principles that come into play? How does this room compare to the perfect one for oration?