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1947-48 Theatre Catalog, 6th Edition, Page 262 (248)

1947-48 Theatre Catalog, 6th Edition
1947-48 Theatre Catalog
1947-48 Theatre Catalog, 6th Edition, Page 262
Page 262

1947-48 Theatre Catalog, 6th Edition, Page 262

THE BlPPLE TANK TEST indicates to the tained physicist or acoustic engineer the acoustic properties of a specific theatre shape. Above is an actual photograph of a ripple tank test of a stage-auditorium model (see explanation in the text): and below is a diagrammatic representation at multiple sound retlections in a horizontal plane as revealed by the ripple. The architect needs the specialist'l help.

capacity house.

Each person in the audience absorbs a certain amount of sound. The unit of absorption is the sabine. If the acoustic specifications for the seats are so drawn that each seat empty absorbs as many sabines at the same frequeincies as the seat plus a person sitting in it, the total

OPTIMUM REVERBERATION TIME, with aetists in place, is shown as a (The curve was developed originally for radio studios, but it is also adaptable to other types of auditorium.) sation tor values within 30 percent of those indicated can be made by

function of studio size.

absorption (and therefore the reverberation time) will be unchanged whatever the size of the audience. Seats and audience are therefore used to keep the reverberation time the same though the audience may vary in size. Before drawing seat specifications it is necessary to look into the question of what kind of

microphone placement. acoustic design' and treatment. (Drawing from an article by I. P. Maxtield Compen- in the Oscillator-copyright 1947 by Western Electric Company. Inc.and used through the courtesy of R. V. Fingerhut and copyright holder.)

people will constitute the audience and how they will dress. An audience of children will have fewer sabines than a matinee audience of women shoppers. Stiff shirts and bare shoulders are reflective as compared to soft shirts and afternoon dresses, a phenomenon which makes the traditional first night audience, at least acoustically, live.

When more absorption than that furnished by the seats or audience is necessary, it is well to get it next from carpet (which serves to eliminate the distraction of noise emanating from the audience), next from decorative hangings which can be changed in position and size, and last from permanent absorbent wall surface materials located so as not to interfere with sound distribution. '


The architect determines his house size from the necessary number of seats; its wall splay and depth from the requirements of. good seeing; ceiling shapes from sound distribution and front stage lighting requirements; back wall and plaster cyclorama shapes by the necessity of preventing echoes and focal points. When model tests confirm the correctness of this much of the design, he may proceed.

His structure is conditioned by the necessity of avoiding resonance (it is generally believed that the organ caused the collapse of the roof in one theatre).

His wall surface and heat insulating materials he specifies to give him: (1) the correct total reverberation time; (2) absorption where and to the extent he needs it.

His ceiling he generally keeps as highly rehective as possible to insure undiminished sound distribution.

He specifies seats which provide the same amount of absorption empty as do seat and occupant together when they are occupied. He insulates the theatre against outside noise and prevents inside noise.

One can count on the fingers of one hand the theatres in which all these requirements have been scrupulously met. N0 theatre in which an honest attempt is not made to meet them is worth building.

Further compensations must be effected through

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1947-48 Theatre Catalog, 6th Edition, Page 262