finalv2ans - 0002-1 Final - Physics 1240 Spring, 2010...

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0002-1 Final - Physics 1240 – Spring, 2010 – version 2 SIL difference (in decibels) Intensity ratio 1 dB 1.3 2 dB 1.6 3 dB 2.0 4 dB 2.5 5 dB 3.2 6 dB 4.0 7 dB 5.0 8 dB 6.3 9 dB 7.9 Bubble in questions 1-40 ON YOUR BUBBLE SHEET! 1. Consider a string on a bass guitar with a fundamental (n=1) frequency of the note we call E2. When you are hearing this 4th harmonic (n=4) of this string, what note are you perceiving? A) E12 B) E7 C) E5 D) E4 E) None of the above corresponds to the 4th harmonic of this string. 2. Consider a giant organ pipe which plays a tone whose fundamental frequency is at the very low end of normal human hearing (which typically ranges from about 20 Hz to 20,000 Hz). Which harmonic number of this pipe is about the highest one most people could perceive? A) Somewhere around n=20,000. B) Somewhere around n=1,000. C) Somewhere around n=200. D) Somewhere around n=10. E) Somewhere around n=3. 3. A native American bass flute is roughly 1 meter long, and is open at both ends. What is the lowest note can be played on this instrument? A) About 340 Hz. B) About 170 Hz. C) About 34 Hz. D) About 1 Hz. E) There is no “lowest note” on an open flute, a highly skilled player can go as low as they want. 4. If you cap off one end of the flute in the previous problem, what happens to the fundamental frequency? A) It goes down by an octave . B) It goes down, but by much less than an octave C) It goes up by an octave D) It goes up, but by much less than an octave E) It stays the same. 5. If the intensity of sound (measured in W/m 2 ) increases by a factor of 5, what happens to the decibel level? A) It goes up by a factor of 20 from whatever value it starts at (decibels are multiplied by 20). B) It goes up by a factor of 5 from whatever value it starts at (decibels are multiplied by 5). C) It increases by +3 dB. D) It increases by +5 dB. E) It increases by +7 dB.
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0002-2 The next few questions are based on the Fletcher-Munson diagram, at right. This diagram helps us understand the connection between pitch, decibels, and perceived loudness (or phons). (The vertical axis in the graph is what we call in our class SIL, or decibel level.) 6. According to the Fletcher-Munson diagram, how many decibels are required for a normal person to just barely detect a 10 kHz tone? A) More than 20 dB B) Between 10 and 20 dB C) Less than 10 dB D) 0 dB E) The diagram doesn't give us the information to figure this out. 7. Suppose I want a recording of a 90 Hz note on a bassoon to have a perceived loudness of 50 Phon. Approximately what SIL do I need coming from my stereo? A) 40 dB B) 50 dB C) 60 dB D) 70 dB E) 80 dB 8. Assume that you go to a very quiet classical concert: at your seat the loudness of all the frequencies in the music is about 60 phons. You record the music, take it home, and crank it on your stereo. Your stereo is set so all frequencies are increased from their original SIL by about +40 dB. Which answer below best describes the change in your perception of the music?
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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.

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finalv2ans - 0002-1 Final - Physics 1240 Spring, 2010...

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