Acousti-Celotex is a brand of acoustical tile technology developed in the 1920s. It was a product of the Celotex Company, which was founded in 1920 by Bror Dahlberg and Carl Muench. The two men had developed a means of turning cellulose waste fibers into a rigid building board, which became a commercial success for their employer Minneapolis and Ontario Paper Company. They established Celotex Company to repeat their success with a fibrous waste of sugarcane refinery.
This instrument, made in the 1950s, was designed to demonstrate the acoustic phenomena of “beats”. Beats are produced when two similar sounds interact. If the sound’s frequencies differ by only a few wavelengths, their combined tone will contain rapid changes in loudness. These are the beats, and they are caused by the physical interaction of sound waves as they alternately combine creatively, to increase the sound, and destructively, to reduce it.
The double siren is an instrument that produces sounds from two sources in a way that allows the phase of one sound to be changed relative to that of the other. It is capable of producing everything in the range of a half-tone to an octave. A double siren consists of two coaxial Dove sirens—disks rotating at high speed. As air flows through a series of holes in each disk, a distinct tone is produced, the frequency of which depends on the rotational speed of the disk, and the spacing of the holes in the disk.
The double siren was one of Koenig’s more popular instruments. It consisted of two “polyphonic” or “multivoiced” sirens with more than one series of holes, and was an invention of the German physicist and former teacher of Hermann von Helmholtz, Heinrich Wilhelm Dove (1803–1879). It produced several pure tones simultaneously, in musical chords, and under greater pressure. It was ideal for demonstrating interference effects (when sound waves combined to amplify or diminish each other) and combination tones. [Pantalony 2009, 184-185]
The Electronic Sackbut, designed by Canadian physicist Hugh Le Caine, is the world’s first known voltage-controlled synthesizer. It employed various techniques in electronic signal processing – among them the generating, dividing, filtering, modulating, and blending of electronically-produced waveforms – to permit new ways of creating and controlling musical sound.
The set of eight tuning forks was acquired by the Science Museum, London, on the closure of the Physics Department of the Royal Naval College, Greenwich. The box is marked “Standard Set of Tuning Forks.” A handwritten note in the Science Museum’s technical file T/1968-634 states that no mention of this particular box of forks can be found in the Museum’s copy of König’s 1889 catalogue (Koenig, R. Catalogue des appareils d’acoustique).
The forks give the notes ciii, civ, div, eiv, fiv, the 11th harmonic of c1, the 13th harmonic of c1, aiv, the 14th harmonic of c1, bv, and cv (ciii and cv have vibration frequencies of 1024 and 4096 respectively).
These forks are constructed to prove the following law:
Koenig’s flame analyser was, next to the sound synthesizer, one of the clearest expressions of Hermann von Helmholtz’s theory that complex sounds were made up of a spectrum of elemental or pure tones. The adjustable resonators covering a range of 65 notes from sol1 to mi5 (96–1,280 Hz), could each be rendered visible with a connection to a manometric flame capsule. The resonators were connected to a gas-filled capsule with a rubber tube. If activated, the distinctive pattern would appear in the rotating mirror.
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