Abstract
The resonance frequencies of a spherical aluminum shell (radius 3.0 in., thickness 1/8 in.) filled with water have been measured for several different values of static water pressure. It is found that a pressure increase of 100 psi causes resonance frequencies associated with axisymmetric bending modes to shift higher by about 0.15%, consistent with predictions of elastic shell theory [DiGiovanni and Dugundji, Air Force Office of Scientific Research Report No. 65‐0640 (1965). The shell is suspended by elastic cords attached to an inlet valve and is excited acoustically with a swept sine wave; the vibrational response is measured with small accelerometers mounted on the shell surface. Techniques for identifying frequency shifts associated with very small pressure changes (less than 1 psi) will be discussed. The effect reported here may have an application in the development of noninvasive methods for measuring intracranial pressure changes. [Work supported by National Science Foundation STEM program and Central Washington University.]
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