Date of Award
Bachelor of Science
Paper Science and Engineering
The objective of this study was to determine the effect of various high frequency sinusoidal strains on the strength properties of a paper cone in a loud speaker. The stresses developed during sound propagation were approximated by applying viscoelastic theories to the paper cone's mode of response. This analysis indicated the stresses developed would be indirectly proportional to the square of the frequency in Hertz. Also relevent is the Boltzmann superposition principle which states that if a second strain is applied before the first strain is dissipated, the resultant strains are additive.
Sets of speakers were operated continuously for 120 hours at three different. frequencies: 100, 1K and 10K Hertz. The power supplied remained constant. An increase in the results of the elongation, folding endurance, TEA and tensile tests and a decrease in the stiffness tests were observed at each frequency. The results indicate that the larger applied shear strain causes a larger variance in the test results. The 10K Hz set yielded a larger variance than the 1K Hz set, implying that the Boltzmann superposition principle is applicable at the higher frequency.
Future work should consider operating speakers for longer time periods and include higher frequencies. These studies could generate more knowledge on the mode of failure and possibly when the added strains would cause a decrease in strength properties that could effect the cone's ability to produce undistorted sound. The extended operation of the speakers could also be compared with the operation of speakers that have been artificially aged to give more insight to the mechanisms of aging.
McQueary, Robert, "The Effect of High Frequency Sinusoidal Strains on the Strength Properties of Paper" (1981). Paper Engineering Senior Theses. 328.