124 SCIENCE OF HOME AND COMMUNITY 



are set in vibration by the fingers instead of by the bow, and 

 the sounding board of the banjo is made of membrane in- 

 stead of wood. 



DEMONSTRATION 14 



Purpose. To study some of the principles underlying the use 

 of musical instruments. 



Apparatus. Tuning fork, sonometer, violin, or guitar. 



Directions. I. Set a tuning fork in vibration. Hold it 

 firmly on the box of a violin or guitar, or on any ordinary box. 

 What difference is there in the sound? What is the use of 

 sounding boards ? 



2. Fasten on the sonometer two strings of the same material 

 but different diameter. Place them both under the same 

 tension. Strike them both and note the difference in pitch. 



3. Fasten two strings of the same size and under the same 

 tension, but of different materials. Strike them and note the 

 difference in pitch. 



4. Use two strings of the same size and material. Put one 

 under greater tension than the other. How do they differ in 

 pitch ? Fasten two strings of the same size and material under 

 the same tension, but have one wire about twice as long as the 

 other. How do they differ in pitch ? 



5. Upon what factors do these experiments show that the 

 pitch of a string depends ? 



[ Wind instruments. In wind instruments the sound is pro- 

 duced by the vibration of air columns. The air may be set 

 in vibration in several ways. In the flute it is set in. vibration 

 by blowing across a hole ; in the clarinet by means of a 

 vibrating reed ; and in the cornet by means of the vibrating 

 lips of the musician. The pitch is controlled in a variety of 

 ways : by changing the length of the vibrating air column, 

 as in the pipe organ ; by blowing gently or hard, as in the 

 clarinet ; by breathing fast or slow, as on the cornet ; or by 

 a combination of several means, as in the flute. 



