EFFECTS OF VIBRATIONS.

Evening Star, Issue 15074, 4 January 1913, Page 6

EFFECTS OF VIBRATIONS.

s~ , Steel rails and wheels are tested by tapping in order to discover if they have any bidden defects. An American engineer has suggested that something of the kind is possible in connection with skyscraper buildings. A representative of the ' New York World'" interviewed' a number of experts in connection with the matter, and obtained some interesting information. The inquiry was based on the assumption that skyscrapers had a certain pitch, tone, and volume which might be ascertained by experiment. Alfred G. Robyn, the well-known organist and composer, answered readily when the query was put to him. " This is not fanciful," said he. il Everything sings—to the musician. You will recall the legend of the blind fiddler and the bridge. He listened patiently at the structure till he caught its vibration or note. Then he reproduced this same note on his violin and fiddled away till lie so increased the vibration of the bridge that it shook itself to pieces and fell with a.crash. —A Dangerous Note.— "That is only a legend. But* here is a Tact. You have perhaps noticed that when a low note of a church organ is sounded the pew you sit in will tremble. In Cincinnati, in the music hall there that contains one of the biggest pipe organs in the country, there is one low note which the organist dares not sound. It causes the entire building to vibrate to such an extent that in the estimation of engineers the safety of the structure would be threatened. Now there you have a concrete instance of the musical note of a building. This low note of the organ was exactly the note of the building. And, as in the case of the fiddler's bridge, the playing of it had a serious disintegrating effect. In giving a concert I always first look carefully over the room. Once, while playing in a private home, I found on testing the piano that it was 'lnpanny' on one note to an amazing degree. The hostess was very much put out, thinking the defect to bo ni the piano. But I found a loose chandelier which responded exactly to the note in question, and the return vibration of which deadened this note, I should say that every skyscraper had a note of its own. And it only remains to have an instrument big and powerful enough to make the building vibrate to its sympathetic note. For instance, it is conceivable that a great steam whistle blowing continuously in the kev of a near-by skyscraper 'would hare some disintegrating effect upon it, especially upon a verv high structure." —Some Experiments.— " Tin's principle of vibration is an elementary one." said Professor W. W. Stiiler. of the Department of Phvsics' Columbia I niversity. ''ln lecture experiments wo use commonly the two timing forks with a common pitch. One set in vibration makes the other sing. Then, if yon stop the first, the other will set it back into vibration again. If you were to take a very delicate glass goblet, get its note, and reproduce this note upon a violin, you could shatter the glass. Everything is in vibration—this table here, this entire building. This is a physical law—that nothing is at rest. In some instances it becomes a serious matter. The vibration of a bridge, for instance must bo carefully guarded, so that it wi 1 not increase to the danger point \\hen nn army nmvos over a bridge the ranks break stop ; otherwise the rhythmic movement would set the bridge, swaying till it might fall apart. I understand that when the circuses <rn over ih.-. Brooklyn Bridge it is customary to have the elephants break step. No-,v, this you might call physical vibration. Sound is air vibration, but it is also physical vibration. You can make one body vibrate by iarring it with another body, like tapping a "rail ! or the movement of troops on a bridge. But you can do the same thing with I sound, provided you hit the right kev." ft