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Sabine, Wallace Clement

acoustics sound hall time

[ sa bin] (1868–1919) US physicist: the founder of architectural acoustics.

A midwesterner from a farming family, Sabine did well as a physics student at Harvard and became an instructor there in 1890. Except for war work in the First World War (he was in effect the first chief scientist for the US Air Force, in 1917–18) he never left Harvard. Some 5 years later Harvard president C W Eliot asked for his help: the acoustics of a major new lecture theatre were so bad as to make it useless. Little was then known of architectural acoustics, but Sabine saw that such problems must arise from the size, shape, and materials of a room, which affect the reverberation time. For speech this should be 1–2 s and for music about 25% longer. In the disastrous new theatre this time was 5.5 s, so that a speaker had the first and last words of a sentence mingled. Since size and shape are not easily altered, Sabine worked on the materials; he and two helpers spent many nights (after midnight, when the street was quiet) moving cushions from another large theatre to the disaster area, making tests, and returning them before dawn. Authority was dismayed by the delay and after 2 years demanded action; Sabine prescribed 22 hair-felt blankets, and the place was rendered usable for the next 75 years.

He had devised an electrically-blown organ pipe and drum recorder to measure reverberation time at 512 Hz, and he now worked hard to develop a formula that would allow calculation of the acoustics of an unbuilt hall. With the aid of more massive cushion-moving experiments, he derived, in 1898, the Sabine formula: T =K V / Sa, where T is the time in seconds for a sound to decay 60 decibels in the hall; K is a near-constant, inversely proportional to the speed of sound; V the volume of the room; S is the total area of all the room surfaces; and a is the average sound absorption coefficient of these surfaces (it varies from about 0.01 for plaster to 1.0 for an open window). With its aid, he was able to advise on a projected new Boston Symphony Hall, opened in 1900. However, musicians were critical of the result; this was probably because an orchestra of 90 sounded thin in such a large hall; today with 104 players the sound is fuller. From 1904 he was much in demand to advise on architectural acoustics, and his methods have been in use ever since.

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