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296                    HAND-BOOK OF ACOUSTICS.
Ans.—See p. 135, and pp. 130 and 134.
9.    What are Tartini's Tones? Ans— See p. 129.
10.    How has difference in the quality of the tone (tone colour) been accounted for ?
Ans.—See p. 74.
11.    Explain the cause of the effect produced by the use of what is popularly called the " loud pedal " of the pianoforte.
Ans.—See p. 95.
Mus.B., Victoria University.
Three Hours.
1.    Describe two different methods by which the velocity of sound has been determined.
Ans. For one method see p. 19. For another method: Stand opposite a wall which gives back an echo. Clap the hands at such a rate that the sounds and their echoes occur at equal intervals of time. Count the number of claps and echoes in (say) 2 minutes. Measure the distance of the observer from the wall. This distance multiplied by the number of claps and divided by 60 will give the velocity of sound.
2.    Taking the co-efficient of expansion of air to be TiT, and the velocity of sound in air at 0° C to be 33200 cm. per second find its velocity at 20° C and 100° 0.
.4»s.—Velocity at 20° C = 33200 */7T~]j[
1 + 273
= 33200 y (If) = 34395 Velocity at 100° s= 33200 a/3^
= 38807
3.    Describe the construction of the siren, and show how it is used to find the vibration number of a given note.
Ans.—See pp. 31 and 32.
4.    Show that the addition of a fifth to a fourth gives an octave.
3 4 2 Ans.- g X 3 = 1
5.    What ought the stretching weight of a wire to be to give a note one-fifth above that of another wire of the same thickness and material, one metre long, and stretched by a weight of 10 kilogrammes ?