File:Bell telephone magazine (1922) (14733191096).jpg

Identifier: belltelephonemag15amerrich (find matches)
Title: Bell telephone magazine
Year: 1922 (1920s)
Authors: American Telephone and Telegraph Company American Telephone and Telegraph Company. Information Dept
Subjects: Telephone
Publisher: (New York, American Telephone and Telegraph Co., etc.)
Contributing Library: Prelinger Library
Digitizing Sponsor: Internet Archive

View Book Page: Book Viewer
About This Book: Catalog Entry
View All Images: All Images From Book
Click here to view book online to see this illustration in context in a browseable online version of this book.

Text Appearing Before Image:
wn asmasking. The effects are somewhat the same as a hearingloss, except that the loss vanishes when the noise is removed.Both forms of audiometers have been used for measuring themasking effect of noise. The noise in an average office in themetropolitan area causes a normal hearing person a loss of 20to 30 db due to masking. In the presence of such a noise, aperson deafened 20 to 30 db would hear as well as an individualof normal hearing. The No. 2A Audiometer has been used by one experimenterto measure the hearing of chimpanzees. They were found tohear as well as but no better than man. Modifications of theaudiometer have been used to test the hearing of cats, guineapigs, dogs and monkeys, in several physiological laboratoriesin this country. Although the opinion is often expressed thatanimals hear better than man, accurate tests of their hearingdo not confirm this. This might be expected since mans hear-ing acuity is near the limit set by the thermal motion of the airmolecules. 8 I
Text Appearing After Image:
Fig. 1. The lA (Left) and 2A Audiometers. AMPLIFIERAND BATTERY MICROPHONE

Note About Images