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ABSTRACTS
The Editorial Office will welcome contributions of abstracts and book reviews from members and subscribers. Contributors to this section are urged to give correct and complete details regarding the reference. Items which should be included in abstracts are:
Title of article
Name of author as it appears on the article
Name of periodical and volume number
Date and number of issue
Page on which the reference is to be found In book reviews, the following data should be given:
Title of book
Name of author as it appears on the title page
Name of publishing company
Date of publication
Edition
Number of pages and number of illustrations
The customary practice of initialing abstracts and reviews will be followed. Contributors to this issue are as follows: G. L. Chanier, Paul E. Sabine, and the Monthly Abstract Bulletin of the Kodak Research Laboratories.
A Method for Estimating Audible Frequencies. W. A. MARRISON. Projection Eng., March, 1930, p. 14. The author indicates a method which permits one to estimate by ear frequencies in the range from approximately 50 to 4000 cycles. If one is not able to recognize a certain pitch without auxiliary means, one should first adopt an approximate standard. The lowest notes one can sing or whistle may be used as such a standard and can usually be relied upon to within 10 per cent. The next step is to learn to recognize musical intervals. The frequency ratios corresponding to the musical intervals are given and the author explains how to use them to find the frequency of any tone in comparison with another of which the frequency is known. A table of equally tempered scale based on AS = 435 is given, as well as the Lissajous figures corresponding to frequency ratios for five different phase angles. The musical intervals are indicated beside the corresponding Lissajous figures. G. L. C.
Sound Theater as an Acoustic Laboratory. J. S. PARKINSON. Ex. Herald World, 97, Section 2, Dec. 21, 1929, p. 38. This is an analysis of acoustical problems in the motion picture theater. Reproduced sound of the human voice presents a different problem from directly spoken sound. A horn is directional, whereas the average speaker's voice is only slightly so. External sound waves are also collected to produce so-called "feed-back" effects with horns. Reverberation in the general sense is defined as the length of time a sound requires to decay to inaudibility. In the author's opinion, there is a universal tendency in theaters
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