Man's physical universe



If a set of similar stoppered test tubes are filled to different heights

with water, tones of different pitch will be obtained when the stoppers

are pulled out from each tube. In this experiment the vibrations are

set up by the rapid expansion of the air produced by removing the

stopper. The amplifier is the column of air in the tube, which, by

resonance, produces tones whose pitch depends on the length of the

air column. Similar differences in pitch can be produced by filling

tumblers to varying heights with water and striking them with a

knife, for example.

The sounds produced in this way do not last long enough to give

good musical tones. Continuous notes can be obtained, however, by

blowing across the tops of test tubes.

In organ pipes and whistles there are channels to guide the air up

to and across the mouth of the pipe.

Air columns are found to give the maximum sounds for vibrations

of certain frequencies only. This is explained by the fact that sound

waves reflected back in a tube may interfere with incoming waves, so

that little or no sound is produced unless the incoming wave is of such

a frequency that it is reinforced by the reflected wave; the column of

air will be caused to vibrate with this frequency, producing an intense

sound. There is a distinct relationship between the length of the tube

and the frequency of the vibration. This accounts for the differences

in the lengths of organ pipes.

In most wind instruments tones of higher pitch, the overtones, may

be obtained by increasing the force of the wind; however, in organs,

the wind is delivered at fairly constant pressure, so that these variations

in pitch are taken care of by a multiplicity of pipes of different

sizes. Some organs have as many as 30,000 pipes.

Drums, cymbals, bells, xylophones, triangles, and similar instruments

depend on vibrations, often of a very complex nature, produced

in rods, membranes, and plates by a blow.

The quality of different musical instruments is

loudness and pitch of the overtones.

determined by the

It is quite possible to analyze the

tone produced by any musical instrument and to determine the loudness

and pitch of each of the overtones present. The Novachord is a

musical instrument that is capable of producing and regulating the

loudness of a large number of overtones along with the fundamental

musical tones.

The Novachord is capable of closely imitating the majority of

musical instruments. About six hundred radio tubes are used in the

Novachord. Nearly perfect imitations of musical instruments could

be produced by instruments based on the principle of the Novachord

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