opeidoscope
(əʊˈpaɪdəskəʊp)
[f. Gr. ὤψ, ὀπ- voice + εἶδο-ς form, image + -scope.]
An instrument invented by Prof. A. E. Dolbear (West Virginia), consisting of a tube closed at one end by a tense membrane, having attached to its centre a small mirror, to show the musical vibration caused by speaking or singing at the open end.
| 1873 A. E. Dolbear in Prescott Sp. Telephone (1879) 262 While engaged in making a manometric flame capsule, I invented the opeidoscope. |