Cinematographic annual : 1931 (1931)

Page scan 000346 from Cinematographic annual : 1931

Record Details:

Title:
Cinematographic annual : 1931
Date:
1931
Publisher:
Hollywood : The American Society of Cinematographers, Inc.
Volume:
Cinematographic annual : 1931
Leaf #:
000346
Language:
English
Subjects:
Motion Pictures, Motion Picture Technology
Collection:
Books
Format:
Books
Contributor:
Media History Digital Library
Sponsor:
{"Media History Digital Library","Richard Koszarski","Jeff Joseph"}
Coordinator:
Media History Digital Library
Description:
Date Added:
June 20, 2024
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250 CINEMATOGRAPHIC ANNUAL In decibels above threshold this is just ten times the logarithm of the ratio of the maintained energy to the energy at zero audibility: 4£ L — 10 logw (2) CAi i = energy density at threshold. From this formula it appears that, if equal conditions of loudness are desired in all theatres, the necessary power should vary directly as the acoustic absorption present. Thus, a theatre having 10,000 units of absorption (corresponding to a volume of about 280,000 40 SO *60 70 CUBE ROOT OF VOLUME -FEET Fig. 2. Optimum Reverberation Time and Cube Root of Auditorium Volume. cubic feet for optimum reverberation) would require a sound reproduction system having twice the capacity of one that was adequate for a house with only 5,000 units of absorption (120,000 cubic feet) . Another slant is that, on the basis of this theory, the same UJ ■>■ Ul -J CD O s ce £ CO t1< o 1 r> o o < s s— — ' J-H-j w J4fi mtrmi 1 — ' — _,>* p^«C_ , — — ^ lllllllll 5^ -— its**^ . . : sp* .ilill 20000 30000 ABSORPTION IN SQUARE FEET Fig. 3. Acoustic Power for Level of 80 Decibels above 4X1 0-10 Microwatts per Square Centimeter as Function of Absorption.