Acustica

This device was built and used by the German physician Chladni (1756-1827), an expert in acoustics, to study the vibrations of the plates and subsequent figures of interference, which can be seen putting some extremely light dust on the plates themselves.

The appliance, sheltered by a wooden case, allows to evaluate, comparing the tones coming from the cylindrical elements it is made of, the upper limit of sounds.

The appliance, if beaten, is the seat of a vibrating movement; it has been used in the 18th century in the first tests concerning the sound.

Bellows with bench and organ pipes (missing) used for acoustics showing tests. The device was built by A.Marloye in Paris, probably in 1850.

The instrument, based on a clockwork mechanism, allows to define a set correspondence between different musical times and the number of the oscillations of a pendulum. Ludwig Van Beethoven was one of the first who used the instrument.

With this instrument it is possible to demonstrate that the pitch of a sound depends only on the number of vibrations in the time unit, that is on frequency. This appliance also permits to measure such frequency; in fact, if we know the number of vibrations made by the wheel per second, and the number of teeth, we may find out the number of hits per second and consequently the frequency.

An appliance, conceived by Charles Cagnard De la Tour (1777 – 1859), which uses the working principle of Seebeck’s siren, with the only difference that the air flux makes the perforated disc rotate and also produces the sound. In 1819 C. Cagnard De la Tour published in “Annales de chimie” an article “ sur la sirène nouvelle machine d’acoustique destinée à mesurer les vibrations de l’air qui constituent le son “. The term siren, which was later on used for all the other analogous appliances, comes from the capacity of the device to work also with a water flux, provided that it is completely sunk.

Seebeck kind siren, rotated by an electric engine so as to produce, because of its rotating speed, high frequency vibrations of the air that hits the holes on the disc of the siren itself.

This appliance, essentially made of a rotating disc with holes, permits to analyze the relationship existing between the rotation speed of the disc itself and the frequency of the acoustic waves produced.

The instrument allows to show quantitatively the laws of Mersenne (1588-1648) concerning the relationship the frequency of vibration of a chord and its length, its tension, the section and the density of the chord itself.

The device is used to study the phenomenon of interference of the sounds produced by a single source.

A device invented by the French physician Jean Marie Constant Duhamel (1797-1872) which allows to record and set the number of vibrations produced by a resonant body.

The tuning-forks are commonly used for the tuning of musical instruments; the commonest type vibrates at 440 Hz, a frequency that corresponds to A in the third scale.

A tuning-fork with a finely carved resonance box.