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Function To use with sounding-pipes. |
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Description It has the form of a table with bellows and a compression room of white skin. The pressure can be increased by hand with the vertical pole that acts on the bag. The communication between the bag and the compression room is established with a brass pipe. Thanks to eight keys we can send the air to the organ-pipes. These are made with open tubes of fir-wood, with a conical entrance adapted to the bellows. | |||
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Function They produce attuned sounds. |
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Description These wooden pieces leaning on few straws give us the musical instrument called xylophone. They are used by letting them fall vertically on a compact floor or on a marble table. | |||
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Function It shows how the sound depends on the length of the pipe. |
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Description In the pipe there is a sliding rectangular section piston with a seal to keep the air in. Because of the relation between length and frequency, this closed tube produces infinity of sounds and, in particular, it gives the notes of the just scale and or of the equally tempered scale in correspondence to the marks in the piston rod. | |||
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Function To study the sound standing waves. |
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Description The pipe has one wall of glass. We place some cork oak, some powder or thin semolina in a little basket with a thin and loose paper-bottom. We slowly drop the basket inside the sounding-pipe with a thread and a pulley placed on the upper end. In the nodes the powder remains in standby, while it leaps and vibrates strongly in the antinodes. | |||
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Function It produces a simple sound without harmonics. |
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Description The fir-wood resonance-box corresponds internally to a fourth of wavelength. The hammer is round with a rubber edge. There are some cursors to modify the sound pitch and to tune two tuning forks perfectly for the resonance or to produce the beats. | |||
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Function To obtain a persistent and constant sound. Record of sinus graphs. |
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Description The apparatus is used to maintain a taut string in vibration or to explain the functioning of the recording chronograph. CC power supply of 4 volt. Duhamel's cylinder. With hand movement but also a with flywheel to action with an electric engine or with a separated clockwork. To register the graphs we can blacken with smoke the brass cylinder or a slightly dampened coated paper leaning on the cylinder. The writing pit must touch the paper very slightly. If we wont to fix the graph permanently, we can strew the paper with a light solution of wax in alcohol or with some common colourless varnish for metals. | |||
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Function To study the sound vibration on a string. |
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Description It is the classical sonometer with the one-metre strings. The mahogany resonance-box, with its upper board and bottom made of fie-wood, is 1,30 m long and rest on metallic feet with a levelling screw. The tension of one of the strings can be obtained by passing the string on the throat of the brass pulley and by applying the lead weights attached to the instrument on the plate. Three white celluloid scales are fixed on the harmonic table: the first is divided into mm, the second with divisions corresponding to the length to give the string to obtain the just scale and the third one with divisions for the equally tempered scale. The three bridges are applied on the protruding scales that are used as their guides. To determine the number of vibrations corresponding to the sound we bring the string to the unison with a known tuning fork. We make the bridge slide until the string reproduces the sound we are examining and we apply the law: the number of vibrations of a string at constant tension is inversely proportional to the length. | |||
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Function They enter in resonance at determined frequencies. |
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Description They are cardboard sounding-pipes calibrated in the just scale of the physicists (that has the 64 hertz UT1 (C1) as its fundamental tone) and they correspond to the eleven harmonics between UT2 (C2) (128) and SOL4 (G4) (768). The seventh and the eleventh harmonics do not correspond to well-defined musical notes. | |||
