PubMed · 5980840
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O J Menzel. 1966. Compression amplification in hearing aids.. https://pubmed.ncbi.nlm.nih.gov/5980840/
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Crosstalk due to coupling produces noise correlation between receiver coils. It has been stated that this correlation reduces the signal-to-noise ratio obtainable from combining signals from the coils. In this paper, it is shown that the effects of crosstalk on the signal-to-noise ratio may in theory be eliminated by properly combining signals. Equations are derived which show how the signals from two coils should be combined in the presence of crosstalk in order to obtain the same signal-to-noise ratio as in an ideal case of no crosstalk. The deviation from optimum signal-to-noise ratio due to imperfect circuits and amplifiers is discussed. An experimental technique for achieving the proper combination of signals is presented.
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The aim of this investigation was to develop a test method that allows an operator to determine the appropriate radiation time for any light-activated material, irrespective of the characteristics of the light-activation unit or material to be cured. A computer-based radiometer was used to monitor the radiation energy transmitted through a number of light-activated materials during irradiation, and a method was devised to determine the predicted radiation time for any given material/shade/light unit combination based upon the change in transmission against time that occurred as the material polymerized. Additional test samples were cured for the predicted radiation times and upper and lower surface microhardness measurements were taken to verify the validity of the test method. Predicted times varied from 16 to 44 s for 2 mm thick samples of the materials/shade/light-activation units used. This method may allow operators to determine appropriate radiation times for any new light-activated restorative they decide to use with their own light-activation unit.