302 COMPOSITION OF SOUND WAVES. 



we had the same reed which was obliged to adapt itself to 

 the different vibrations of the different air columns. 



(a.) It will be easily seen how reeds may be used in musical in- 

 struments. The accordeon, clarionet and vocal apparatus are reed 

 instruments. 



471. Effect of Lateral Openings* Certain 

 wind instruments, like the flute, fife and clarionet, have 

 holes in the sides of the tube. On opening one of these 

 holes, opportunity is given for greatest amplitude at that 

 point. This changes the distribution of nodes, affects the 

 length of the segments of the vibrating air columns, and 

 thus determines the wave length or pitch of the tone. 



EXERCISES. 



1. If a musical sound be due to 144 vibrations, to how many vibra- 

 tions will its 3d, 5th, and octave, respectively, be due ? 



2. Determine the length of a tube open at both ends that can 

 resound the tone of a tuning-fork vibrating 512 times a second. 



3. A certain string vibrates 100 times a second, (a.) Find the 

 number of vibrations of a similar string, twice as long, stretched 

 by the same weight. (&.) Of one half as long. 



4. A certain string vibrates 100 times per second. Find the num- 

 ber of vibrations of another string that is twice as long, and weighs 

 four times as much per foot and is stretched by the same weight. 



5. A musical string vibrates 200 times a second. State (a.) what 

 takes place when the string is lengthened or shortened with no 

 change of tension, and (6.) what change takes place when the ten- 

 sion is made more or less, the length remaining the same. 



6. A tube open at both ends is to produce a tone corresponding 

 (.) to 32 vibrations per second. Taking the velocity of sound as 

 1120 ft., find the length of the tube. (&.) If the number of vibra- 

 tions be 4480, find the length of the tube. 



7. (a.) Find the length of an organ pipe whose waves are four 

 feet long, the pipe being open at both ends. (&.) Find the length, 

 the pipe being closed at one end. 



8. A tuning-fork produces a strong resonance when held over a 

 jar 15 inches long, (a.} Find the wave length of the fork. (6 ) Find 

 the wave period. 



