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American Research on Acoustics

Abstract

THE Wallace Sabine laboratory of acoustics, a photograph of which is here reproduced (Fig. i) is situated at Geneva, Illinois. It is a three-story building of brick and concrete specially erected for its purpose and forms a unique design, consisting of two structures under one roof, an inner room or sound chamber completely insulated from an outer shell. Figs. 2 and 3 show a plan and section of the building, the main feature of which is the sound chamber 27 ft. by 19 ft. and 19 ft. io ins, high. Here the original intensity of the sound is measured. The walls of this chamber are of 18-inch brick coated with cement outside and with wood fibre plaster inside, and the room as shown in the section has a separate concrete foundation. From this room half-way up Fi(;..-Riverbank laboratories, Geneva, Illinois. its walls three small testing chambers are provided furnished with heavy steel doors to exclude sound completely. Materials to be tested are placed across these chambers, when the doors are opened to admit sound from an organ in the sound chamber. The organ is a complete 73 pipe instrument giving all the tones of the musical scale from C 64 to C 4096. It is operated electrically by the observer, who notes the time before a sound becomes inaudible in the test chamber. To ensure equality of sound distribution in the sound chamber a large steel reflector mounted on a central shaft is made to revolve in the room on a vertical axis. The main work, up to the late Prof. Sabine's death, has been connected with the calibration of the sound chamber and its instruments. This laborious undertaking completed, the activities of the laboratory should rapidly command a wider interest.

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