256 HAND-BOOK OF ACOUSTICS.
144. To what length (approximate) muot an open organ pipe be cut to produce the F' on the top of the Treble staff? To what length, if stopped ?
145. What is the general effect of rise of temperature upon organ pipes, and why has it this effect ?
146. I have two organ pipes, one of metal and the other of wood. They are exactly in unison on a cold day in winter, while on a hot summer's day they are out of tune with one another. Explain the reason of this. Which will be the sharper of the two in warm weather ?
147. How is the pitch of a pipe affected by the wind pressure ?
148. Detail the various circumstances that affect the pitch of an organ pipe.
149. Why cannot the intensity of the sound from an organ pipe be increased by augmenting the wind pressure ?
150. Describe the two kinds of reed used in musical instruments, and explain their action.
161. Explain why the tones of a harmonium are so rich in partials.
152. What is the function of the pipe in an organ reed-pipe ?
153. How are reeds sharpened and flattened ?
154. What is the effect of a rise of temperature on the pitch of a reed ?
155. What is the cause of the peculiar quality of the tones of the Clarionet P
156. Describe the principle of the French Horn, showing the origin of its Tones, and how variation in pitch is effected.
157. To what class of instruments would you assign the Human Voice, and why ?
158. What circumstances affect the production of partials, and therefore the quality of the tones of the Human Voice ?
159. I sing successively the vocal sounds " a" and " oo;" state briefly the changes that take place in the shape and size of the mouth, in passing from the former to the latter; and show how these changes cause the difference in the above sounds.
160. By increasing the wind pressure in blowing the Flute, the tone rises an octave; in the Clarionet, it rises a Twelfth. Explain this discrepancy.
161. State the laws connecting the vibration number with the length of a rod, vibrating longitudinally—
1st. When the rod is fixed at both ends. 2nd. When it is fixed at one end only. 3rd. When it is free at both ends. 1616. What partials may occur in each of the above cases?