. Annual report of the Board of Regents of the Smithsonian Institution. Smithsonian Institution; Smithsonian Institution. Archives; Discoveries in science. 354 i)K. K(i:ni(i s kivskakches on from wliicli wind issues, the inaxiimini (lisi)laceinent of air will result when the slit is least covered, or wheu the point of greatest depression of the curve crosses the front of the slit. The negative ordinates of the curve correspond therefore ai)proxiinateIy to condensations. Air is. Fig. 7. now being supplied to the slits; and when I open one or other of the valves which control the air passages, y
. Annual report of the Board of Regents of the Smithsonian Institution. Smithsonian Institution; Smithsonian Institution. Archives; Discoveries in science. 354 i)K. K(i:ni(i s kivskakches on from wliicli wind issues, the inaxiimini (lisi)laceinent of air will result when the slit is least covered, or wheu the point of greatest depression of the curve crosses the front of the slit. The negative ordinates of the curve correspond therefore ai)proxiinateIy to condensations. Air is. Fig. 7. now being supplied to the slits; and when I open one or other of the valves which control the air passages, you hear one or other of the sounds. It must be audible to everyone present that the sonnd is louder and more forcible with a difference of phase of \ than in any other case, that produced with ^ difference being gentle and soft in tone, whilst the curves of phase 0 and ^ yield tones of intermediate quality. Dr. Kcenig found that if he merely combined together in various phases a note and its octave (which was indeed the instance examined by me binanrally in 1876), the loudest resultant sound is given when the phase difference of the combination is ^, and the mildest when it is ^. Returning to Fig. 6, in the second line are shown the curves which result from the superposition of the odd members only of a harmonic series of decreasing am[)litude. On comparing together the curves of the four separate phases, it is seen that the form is identical for phases 0 and i, which sho\v rounded waves, whilst for phases ^ and '} the lbrn)S are also identical, but with sharply angular outline. These two varie- ties of curve are set out on the two edges of the highest metallic cir- cumference in the apparatus depicted in Fig. 7. The angular waves are found to yiebl a louder and more strident tone than the rounded waves, though, according to von Uelmholtz, their tones should be aiike. A much more elaborate form of compound wave siren was constructed by Dr. K^nig for the synthetic study of these
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