DATA DRIVEN 1D - MODAL DISPERSION ESTIMATION IN HYDRAULIC FLUID MEDIA

Document Type

Conference Proceeding

Publication Date

1-1-2024

Abstract

Acoustics are commonly analyzed using a source-pathreceiver paradigm, in which the source and receiver are often pre-determined by design requirements. Consequently, the characteristics of the path typically have the most significant effect on the acoustic profile developed by a dynamic system. In particular, the wave propagation characteristics of the medium are critical for analyzing the propagation of noise through a system. As a result, understanding the behavior of wave propagation within a medium is essential to characterize the acoustic properties exhibited by a system. The most relevant of these characteristics is the speed at which a wave propagates, which can be derived from the relationship between spatial wavenumber and cyclic frequency. Current testing approaches rely on time-of-arrival, or "Pitch and Catch", analysis which is limited to higher frequencies where reflection from boundaries does not interfere with time estimation. To accurately estimate arrival time, a sufficient number of wavelengths are required between measurement locations to allow measurable time to pass. This results in cumbersome and impractical testing conditions that are often unobtainable for low frequency measurements. To experimentally determine the relationship between wave number and frequency without relying on time-of-arrival methods, estimated acoustic mode shapes can be utilized to compute their spatial wave number. This wave number is plotted against the corresponding resonance frequency to form a dispersion curve. Multiple harmonic modes are measured to more accurately estimate dispersion properties across a range of frequencies. Acoustic modes are measured using a variable position hydrophone within a medium-filled wavetube to capture adequate measurements for dispersion estimation. Such a method removes the necessity for multiple wavelengths between measurement locations and allows for measurements to be taken at the lowest resonance frequency of the wave tube, enabling a compact test bench that can be utilized across a wider range of frequencies and mediums. By taking advantage of standing waves within a wavetube rather than avoiding them, a simpler testing method can be employed to extract clearer dispersion information across more frequencies than traditional estimation techniques.

Publication Title

Proceedings of ASME 2024 Conference on Smart Materials, Adaptive Structures and Intelligent Systems, SMASIS2024

ISBN

[9780791888322]

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