Questions and Problems

Author: N.H. Crowhurst

1. What two kinds of air movement combine to produce sound waves? Illustrate with a wave started by bursting an inflated paper bag.

2. What two properties of air (or any other medium through which sound travels) control propagation velocity of sound waves?

3. How does the speed of sound change with (a) barometric pressure, (b) atmospheric temperature? State any approximate rule that can be used,

4. State why you think sound waves travel faster in steel than in iron or brick,

5. What part of (a) a piano, (b) a violin, is responsible for radiating sound waves into the air?

6. Explain the relationship (a) between frequency and pitch, (b) between intensity and loudness. What frequency interval corresponds with a pitch interval of one semitone in music?

7. What is the ratio between intensities corresponding to (a) the full range of average human hearing, (b) the smallest change in loudness that can be detected with very careful listening?

8. How would Question 7 be answered in decibel units?

9. How does Fechner's Law explain the usefulness of the decibel scale?

10. Why do potentiometers for use as volume controls have a logarithmic gradation?

11. What are the three basic properties of a musical tone? On what properties of sound does each of these properties depend?

12. Why can a string vibrate at more than one natural frequency? Explain the relationship between the different frequencies at which it can vibrate.

13. Why do you think strings for the lowest notes on the piano are "loaded" by having a spiral of wire wound on over the central stretched one?

14. Suggest why the same violin, played by an accomplished musician, gives a much sweeter tone than when played by a novice.

15. What is the basic difference in the overtone structure of organ pipes with the "far" end open or closed?

16. If the same pipe is provided with a removable end plug, how will its pitch change from open to closed?

17. Why is it that a narrow organ pipe sounds thin or reedy, while a wide pipe gives a deep, smooth tone?

18. What are standing waves? Explain how they build up inside (a) a closed and (b) an open organ pipe.