Acoustic Spectrum of Beam Elements in Pulsatile Flow: Toward Material-Property Detection for Heart Valve Diagnostics

Heart valve sounds arise due to the vibration of the leaflets, vessel walls, and pressure fluctuations within the flow itself. Knowledge of the frequencies present due to valve geometry and thickness would enable prediction of how restricted a valve is based on the acoustic spectrum. This study investigates pulsatile flows with simple free-standing rectangular beam elements of varying size that are placed crosswise in the flow. Beam elements will have predictable vibrational modes and vortex shedding frequencies based on their geometry, material properties, and flow velocity. First, the elastic properties of the beam material are experimentally characterized. Next, a series of pulsatile flow experiments are performed that vary the flow rate and beam geometry. The flow spans differing Reynolds numbers with a set Womersley number that matches physiological conditions, while contact microphones with a flat frequency response from 1 Hz to 20 kHz capture sound signals over multiple pulsing cycles. The acoustic spectra, spectrogram and bicoherence maps are compared across beam configurations to discern whether predicted frequencies are present in the signal. Tracking how the spectral peaks and phase-coupling shift with beam geometry provides insight into what parameters affect the sound signals, enabling future work in separating structural information from leaflet-generated noise in heart valve studies.