Infrasonic Resonances in Natural Underground Cavities

Abstract

Several examples of acoustic resonance in the frequency range from 0.001 to 1.0 Hz have been observed in limestone caverns. In some cases, the cavern geometry is simple enough for direct application of the Helmholtz resonator theory, and good agreement is found. Three experiments are described. Spectral analysis indicates that subacoustic resonance is responsible for numerous reports of periodically fluctuating or reversing cavern winds, and that appropriate wind measurements can provide new information about chambers not accessible to exploration.