File:Hearing acuity test in anechoic chamber 1949.jpg
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| Description |
English: Hearing acuity experiments at AT&T in 1949. The test subject sits in an anechoic chamber in front of a high fidelity speaker. Sounds differing slightly in loudness and pitch are played, and she indicates which is louder by pressing a button in her hand. A tube in her ear canal conducts sound to a condenser microphone to monitor the intensity of sound actually reaching her eardrum. The subject and apparatus are supported on a metal screen in the center of the chamber, as a solid floor would disturb the sound patterns. The bass speaker at bottom is a folded horn speaker, with a multicell horn tweeter on top. |
| Date | |
| Source | Retrieved February 14, 2015 from Radio-Electronic Engineering magazine, Ziff-Davis Publishing Co., New York, Vol. 20, No. 5, May 1949 , p. 99 on http://www.americanradiohistory.com |
| Author | Unknown author |
| Permission (Reusing this file) |
This image is from an advertisement for American Telephone and Telegraph Co. without a copyright notice published in a 1949 magazine. In the United States, advertisements published in collective works (magazines and newspapers) are not covered by the copyright notice for the entire collective work. (See U.S. Copyright Office Circular 3, "Copyright Notice", page 3, "Contributions to Collective Works".) Since the advertisement was published before 1978 without a copyright notice, it falls into the public domain. |
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This work is in the public domain in the United States because it was published in the United States between 1929 and 1977, inclusive, without a copyright notice. For further explanation, see Commons:Hirtle chart as well as a detailed definition of "publication" for public art. Note that it may still be copyrighted in jurisdictions that do not apply the rule of the shorter term for US works (depending on the date of the author's death), such as Canada (50 p.m.a.), Mainland China (50 p.m.a., not Hong Kong or Macao), Germany (70 p.m.a.), Mexico (100 p.m.a.), Switzerland (70 p.m.a.), and other countries with individual treaties.
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| Date/Time | Thumbnail | Dimensions | User | Comment | |
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| current | 02:37, 16 February 2015 | | 1,020 × 820 (167 KB) | Chetvorno (talk | contribs) | User created page with UploadWizard |
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